I have a new HTC Evo 4 Shift. I subscribed to Sprint TV and now ALL of my data on my SD card is gone, including the formatting. I contacted Sprint Technical Support and they have never heard of this. Tried resetting the phone, still nothing. Their only advice? Go to a Sprint Store and buy a new data card. ARE THEY KIDDING ME?? I have had Sprint for over 10 years and am a Sprint Premier customer and that's all they can tell me is "Sorry your data got erased. Go buy another card." IT'S A 16GB card!!! WTF???
If the data's been deleted then nothing can be done to get it back, but for what it's worth I recommend you never keep important data solely on your phone. Your phone can get wet, lost, stolen, or things like this can happen - especially if you're using a faulty SD card. Always keep a full copy of any important data on your computer.
For the occasional data generated on the phone itself (like camera photos), dump them off to a computer often, or if you can't, get a Dropbox account that syncs your files to an online storage location that's unlikely to ever be lost:
There are software programs that can recover data on SD cards that have been erased. One program I've used is Recuva.