| Unfortunately, file recovery programs seem to all deal with undeleting
| DELETED files, and in this case nothing has been deleted. I expect the
| problem is a corrupted file allocation table because every computer I
| put the USB drive in tells me the drive has not been formatted,

Any partitioning program should be able to recover
corrupted or deleted partitions, which then makes
the files available. I'm not sure about USB sticks, though.
I have one stick that's not seen at all in one particular
Win7 laptop. I have no idea why. I don't trust them with
anything other than moving files from one place to another.