Locking the card is something that ALWAYS should be done before inserting it into a reader. The finder can cause a problem, this simple thing protects against that happening. The fact that the files are 32K is troubling. Have the card(s) been erased? Did you do a compare of the size of the folder that was copied with the folder on the card, this is a must do, it is the quickest verification of the copy.
Do a check check of the folder with all the files in it, what is the total capacity of the folder?
If the files are still on the card, are the movie files 32K on the card? Will they playback in the camera? Have you tried other software like VLC to try to play the movies?
BTW, the thumb nail file is not needed to pay the file or use it. It is needed if you hack the EOS Log and Transfer plugin to work with the T2i. But you really want to copy the entire folder structure as is, into each own folder on the HD.