Blogger Kent Brewster used previously mentioned file recovery utility PhotoRec to rescue an unreadable thumb drive. He writes:
PhotoRec ignores the file system in favour of finding lost files, so it works on FAT, NTFS, EXT2/EXT3, HFS, and (with certain caveats) ReiserFS. And since it's looking for known file headers and using data carving techniques, more than eighty file types—among them DOC, PDF, and PPT—are instantly recoverable.
And recover all the files on Kent's USB drive PhotoRec did; all he had to do was rebuild the directory structure and rename the files.