If a 6 year old could do it in Photoshop, then the same 6 year old probably could undo it too. Just run the distortion with opposite paramaters (shrink where you stretched, and stretch where you shrank) and you end up with the original image again.

I seem to recall a few years ago, a police agency cracking a child pr0n case by undoing a distortion made on the perpetrator's face in the images.

This sort of thing usually happens around once per year. Not as odd as you'd think.