The other day my photos disappeared and I saw that the sd card wasn't registering. How can I get it back? Have removed and replaced it, turned off and on again, mounted it, but still nothing.
Put it into a card reader, plug the card reader into your computer (Linux, Mac or Windows) and run PhotoRec on it. (Instructions are at PhotoRec Step By Step.)
Then send a nice Thank You email to CG Security. They could easily charge lots of money for this program.