Why did I lose some pics during "cut and paste" on my pc?

Hi there. Last Tuesday, I was passing my photos from the phone to the pc, when I realized that some pics went missed and I can't find 'em anymore on the iPhone nor in the pc's file. The loss just includes some of the pics because I just can't find a hundred of them (from 5000 to 5126) and I can't explain why I experience such a tragic and strange bug. Anyone has already been through this? Does exist a software or something like that that might help me recover my lost pics from the phone or from the computer? Please help me out, if you can.