If the file was encrypted, you’re probably SOL. If it was not encrypted it may be possible to to recover some parts of the files. This is extremely advanced level data recovery. I only know the abstract basic principals and would likely struggle to figure this out and recover my own stuff if I ever needed to do this. I’ve only programmed microcontrollers and flash memory devices.

A micro SD card contains a small microcontroller and some blocks of flash memory, although the microcontroller is transparent to the user and operating system… unless hacking with needle probes in a lab.

So here’s the basics. Writing flash involves taking an entire Page of memory and zeroing it first. There is a tiny voltage booster circuit on the card that allows the page to get pulsed up and down in voltage a few times in order to completely zero the entire page without any remaining residuals. Once this is done and the entire page has been zeroed, only then is it possible to write the data into the bytes of the page.

If you want to change a single byte level value in an address that already contains a value, first the entire page is copied to a blank page in another location, then the old page is pulsed a few times, then each value is transferred back into the old page except that the new value that needed to be changed is now set to the new values.

This is the proper way to write flash at a basic level. If the power is lost in the middle of this cycle, the worst case scenario is that the new updated value was not written. The page in question should never be “missing” because the header record should always point to either the original or copied page. One of the two should always be present and complete… in a proper setup. Obviously, it might be faster to simply use some RAM to hold the page, erase the old page and rewrite it. I have no idea what size pages are in modern SD cards, but on hobby class microcontrollers I have used the pages were 4096 bytes, IIRC. My understanding is that most SD cards use an 8051 clone micro, so it is probably a similar size.

So here’s the thing, the bulk of the data is always there. Somewhere deep down inside you likely already knew this. It is why you’re supposed to overwrite an entire drive instead of the “quick” erase in most formatting tools. The quick erase is simply deleting a tiny header file that says what exists where on the drive. Similarly, some part of your SD card there is a page or few where the header has been screwed up. Your OS is looking at this header info and seeing a mismatch of garbled junk and saying f-that bs.

Generally, recovery would involve dumping the raw contents of the flash memory as hexadecimal, being super familiar with what you’re looking at and knowing how to find the page that is causing the error. Generally I assume you’d need to replace the bad page with a good header and it would then work. There are services for this kind of operation; data recovery. In practice, this has a few more layers of complication. Pages can be placed in different locations that enable wear leveling so one area of memory is not over utilized. There is also a table of bad blocks/pages that the micro knows to skip, and there is usually a bit or address in the page that is used to detect errors that may have occurred.

This is pretty much everything I know on the subject. Hopefully it helps you understand the abstract nature of what is happening. In the simplest of terms, flash memory is like writing a long essay with an ink pen and where you can not make mistakes or use whiteout. If you need to make a change, you must write out the entire page all over again. This process is what is so time critical that you must “eject” the drive.

For instance, the base Android system AOSP is designed to use Linux kernels that are prepackaged by Google. These kernels are well documented specifically for manufacturers to add their hardware support binary modules at the last possible moment in binary form. These modules are what makes the specific hardware work. No one can update the kernel on the device without the source code for these modules. As the software ecosystem evolves, the ancient orphaned kernel creates more and more problems. This is the only reason you must buy new devices constantly. If the hardware remained undocumented publicly while just the source code for modules present on the device was merged with the kernel, the device would be supported for decades. If the hardware was documented publicly, we would write our own driver modules and have a device that is supported for decades.

This system is about like selling you a car that can only use gas that was refined prior to your purchase of the vehicle. That would be the same level of hardware theft.

The primary reason governments won’t care or make effective laws against orphaned kernels is because the bleeding edge chip foundries are the primary driver of the present economy. This is the most expensive commercial endeavor in all of human history. It is largely funded by these devices and the depreciation scheme.

That is both sides of the coin, but it is done by stealing ownership from you. Individual autonomy is our most expensive resource. It can only be bought with blood and revolutions. This is the primary driver of the dystopian neofeudalism of the present world. It is the catalyst that fed the sharks that have privateered (legal piracy) healthcare, home ownership, work-life balance, and democracy. It is the spark of a new wave of authoritarianism.

Before the Google “free” internet (ownership over your digital person to exploit and manipulate), all x86 systems were fully documented publicly. The primary reason AMD exists is because we (the people) were so distrusting over these corporations stealing and manipulating that governments, militaries, and large corporations required second sourcing of chips before purchasing with public funds. We knew that products as a service - is a criminal extortion scam, way back then. AMD was the second source for Intel and produced the x86 chips under license. It was only after that when they recreated an instructions compatible alternative from scratch. There was a big legal case where Intel tried to claim copyright over their instruction set, but they lost. This created AMD. Since 2012, both Intel and AMD have proprietary code. This is primarily because the original 8086 patents expired. Most of the hardware could be produced anywhere after that. In practice there are only Intel, TSMC, and Samsung on bleeding edge fab nodes. Bleeding edge is all that matters. The price is extraordinary to bring one online. The tech it requires is only made once for a short while. The cutting edge devices are what pays for the enormous investment, but once the fab is paid for, the cost to continue running one is relatively low. The number of fabs within a node is carefully decided to try and accommodate trailing edge node demand. No new trailing edge nodes are viable to reproduce. There is no store to buy fab node hardware. As soon as all of a node’s hardware is built by ASML, they start building the next node.

But if x86 has proprietary, why is it different than Qualcomm/Broadcom - no one asked. The proprietary parts are of some concern. There is an entire undocumented operating system running in the background of your hardware. That’s the most concerning. The primary thing that is proprietary is the microcode. This is basically the power cycling phase of the chip, like the order that things are given power, and the instruction set that is available. Like how there are not actual chips designed for most consumer hardware. The dies are classed by quality and functionality and sorted to create the various products we see. Your slower speed laptop chip might be the same as a desktop variant that didn’t perform at the required speed, power is connected differently, and it becomes a laptop chip.

When it comes to trending hardware, never fall for the Apple trap. They design nice stuff, but on the back end, Apple always uses junky hardware, and excellent in house software to make up the performance gap. They are a hype machine. The only architecture that Apple has used and hasn’t abandoned because it went defunct is x86. They used MOS in the beginning. The 6502 was absolute trash compared to the other available processors. It used a pipeline trick to hack twice the actual clock speed because they couldn’t fab competitive quality chips. They were just dirt cheap compared to the competition. Then it was Motorola. Then Power PC. All of these are now irrelevant. The British group that started Acorn sold the company right after RISC-V passed the major hurtle of getting past Berkeley’s ownership grasp. It is a slow moving train, like all hardware, but ARM’s days are numbered. RISC-V does the same fundamental thing without the royalty. There is a ton of hype because ARM is cheap and everyone is trying to grab the last treasure chests they can off the slow sinking ship. In 10 years it will be dead in all but old legacy device applications. RISC-V is not a guarantee of a less proprietary hardware future, but ARM is one of the primary cornerstones blocking end user ownership. They are enablers for thieves; the ones opening your front door to let the others inside. Even the beloved raspberry pi is a proprietary market manipulation and control scheme. It is not actually open source at the registers level and it is priced to prevent the scale viability of a truly open source and documented alternative. The chips are from a failed cable TV tuner box, and they are only made in a trailing edge fab when the fab has no other paid work. They are barely above cost and a tax write off, thus the “foundation” and dot org despite selling commercial products.