The basic rule when attempting rescue of lost, damaged or deleted digital photo files is to always begin your search in the last place the file was located whole and intact. Very often people attempting photo recovery make the mistake of searching for the files lost in the target destination of the file download. In camera to computer situations this will be your computer hard drive. But even when the majority of the file transfer has been correct, those files lost due to an interruption of data transfer will never be recovered from the hard drive.
One must backtrack to the camera itself and the memory card or SD card within it. This type of digital photo file recovery is accomplished using an operating system specific recovery utility, meaning that for Windows photo recovery use a PC supported tool. For photo recovery on Mac computers use a program built to run on Mac OS X.