I can't find pictures taken and stored in my camera

I forgot to reinsert my memory stick in my S730 Samsung camera. I took three pictures, saw them in preview mode, then when I tried to download them to my picture file, I got "card error" with no pictures shown. Earlier I saw a bunch of pictures taken several weeks earlier still on my camera. Where where they stored if the memory stick was not in the camera. Now I can't get any of my pictures, neither the older ones nor the newer ones. What do I do to recapture these pictures.