Try restarting ID (and if the file is stored on the flash drive, make sure it is still plugged in). If you are lucky, the file is not corrupt and the auto-recovery will work.
Working directly off a flash drive is very risky. Best practice is to copy what you need to the hard drive, edit and save, then copy back to the flash drive.
It did not even save on my flash drive.
Did you try restarting ID? It may still auto-recover a never-saved file.