why does my 16gb SDHC card reads as full, but I can't see the files

I have a SanDisk 30mb/s 16GB SDHC card used with a GoPro HD Hero. When I plug it into my card reader, it DOES show up on my desktop. When I double-click on it, I see the folders, but no files. I know the card is full, and it shows up as full when I press "command i".

How can I get these files?!?