I can't recall what it was, but there was a cab I installed not too long ago that ganked my files but when I looked at them via a different card reader the space was the same but there were only a few files. Almost like it corrupted them to the extent the couldn't be viewed even in explorer. Let me think on it and maybe I'll be able to remember the program to see if you might have it installed but I eventually formatted my card again since I frequently store .nbh files on it to re-flash the ROM. If you don't already backup (I know you've heard the preaching before, but everyone messes up once or twice LOL That's how we learn
), try MobSync because it will let you backup directories unlike activesync which is point and click each file. Here is the Mobsync .zip and I will see if I can refresh the gray matter to remember the program. I would also try a recovery option or DOS if you can. Sometimes you get lucky and the files are alright
Good luck! Thank me if I helped.