Digital cameras: Digital Camera - Pictures disappeared

Vanishing Digital Photo Mystery

I repair digital cameras and it sounds like you might have a second folder that was created on your card when you changed batteries. Most of the missing shots might be in this other folder. The only way to view this properly is to load it into your computer via a card reader and open it like a hard drive. it would reveal more than one folder in your root directory.

Another possibility is the bad one. The buffer memory on your camera could be failing. This is the memory that is used to temporarily store the images captured by your CCD so that they may be processed with the proper white balance, sharpness and tone settings befor being stored onto your removable card.
This memory is usually part of the CCD circuit in cameras under $500 and is costly to replace.

Then again, I would check for bent or dirty pins in the removable card slot where your memory card is inserted. There are contact cleaners and straighteners on the market that can safely clean and restore alignment to the delicate pins that mate with your particular type of memory card. One pin that is dirty can actually allow you to see captured images on your LCD screen, because the camera senses that the card is in place, but never allow the image to store on the card because the write or read signal is not enabled.