So these files were on the flash drive and you just tried to move them to a new directory?

I'd probably first go to a Linux machine (download a Live CD if you have to) and create an image of the filesystem on the flash drive ("cp /dev/sdc /tmp/flash.fs" or something like that, depending on how the Linux machine sees the flash drive) and then work with that image.

However, if the files were on your hard drive and they're now gone, the first thing you want to do is not create any new files. You might still be able to undelete the files using an undelete utility. (I don't think this is what you meant, though.)