I accidentally deleted important documents (about 100 PDFs) that weren't backed up yet from a 64 GB microSD card, which is used as the primary storage in my unrooted Android 9.0 smartphone. The microSD card is not encrypted and quite new, but for some reason, I've never been able to access the card from any PC when plugged into a card reader - only through the smartphone or when the phone is connected to the PC via USB and only using the MTP protocol. Under Windows, I always get the error message that the card needs to be formatted first.
After the accidental deletion, the microSD card was immediately removed from the phone, so I'm fairly certain that the files are still "healthy". I hope Android and SD cards work the same way as other OSs and common file systems in that normal deletion does not physically remove the data from the storage device, but only from the file table (please correct me if I'm wrong).
QUESTION: How can I restore my deleted files? Also, is there a way to get RAW access from a PC?
Any idea why I can access the card only via the MTP protocol from Windows?
For hard drives/storage devices accessible from a Windows or Linux PC, I've been using several recovery programs with mixed success in the past, e.g. Piriform's Recuva, CGSecurity's PhotoRec, and recently also RecuperaBit. I do have the Android SDK platform tools installed and have used ADB before to uninstall apps etc. if that helps. But I have zero experience with this data recovery problem on Android - and I'm also confused why e.g. Windows won't read the card's contents when connected via a card reader.
Small correction: My poor choice of words seems to have caused some confusion. By
used as the "primary storage"
I didn't mean to say that Android is running the system partitions (
data etc.) on the SD card instead of the internal memory. Rather, all apps are set to store their data on the SD card if possible in order to prevent irretrievable data loss in case of a phone brick. This is due to very bad past experiences with Android's security architecture, which is basically a trap waiting to lock users out of their own data.
Furthermore, I can confirm that SD card encryption is an optional setting in my Samsung's Android 9.0 and has not been turned on. Hence, the SD card ought to be unencrypted!
Sorry for not being clearer.
Here is a screenshot of DMDE showing relevant partition information: