I carelessly installed OSMC on my USB thumb drive instead of the SD card. USB drive had important stuff on it. I have not put the USB drive in Kodi. Is there a way to get back the data on my USB drive?
I am guessing it re-partitioned my USB drive to a different file format?
I used a file recovery program to get some files back, but lost all the file names. Is there a way to restore the entire partition?
It mentions a “go back” option, or something like that, when you first put an SD card in the RPI. However, not sure what to do with USB stick.
The author of the guide you are following is somewhat confused. The OSMC installer prepares the SD card for installation. It only ever needs to write to the SD card regardless of what type of install you are doing, it just does different stuff to the SD card depending on your choices.
If you wanted to perform a USB install, then you prepare the SD card on the PC/Laptop/Mac and then insert your SD card AND USB stick into the Pi. Upon booting, after giving you one last warning and a 60 second timeout only then does the USB get overwritten.
If sounds like your issue is that instead of writing files to the SD card with the installer you wrote files to the USB stick. There are some warnings in place to try and prevent this but in your case they didn’t appear sufficient.