"Accidental deletions are the bane of our digital existence. We’ve all been there, whether due to careless editing or being too quick to format a memory card.
The good news is, deleted files can usually be recovered with a fairly high success rate — that doesn’t mean it’ll always work, though. (It helps if you’re using the right SD card.) There are two specific programs, for Windows and OS X, that you’ll want to pay attention to...."