You could take the card to Wolf Camera or any other professional camera stores to see if they can find any on the card...or there might have been something weird on your computer and they are saved in another file, that has happened to me once or twice before and never could figure out why.
One thing that you need to make sure you're doing is reformatting the card every time you put it back in your camera...check the manual for details on how to do that. The other thing you NEVER do is delete the pics off the card before you can verify that they are safely on your computer. Back up CDs are always a safe bet too.
Good luck!