Are you overclocking your phone in any way, shape, or form? I've noticed that if I have my phone overclocked to anything above 700-ish Mhz, the SD card unmounts itself on occasion and then everything is screwy after that. If you have a Micro-SD-to-SD card, plug it in to your computer; see if you can get Recuva to work on it. Otherwise, I don't know what to tell you; you could search on Lifehacker or Reddit for "data recovery", and you might find something there.