I had something to happen to my Scandisk 32 GB class 6 SD card, over the weekend. When I unlocked my phone, I got a notification that my SD card was unmounted. (Even though I didn't do it.) All the apps I had moved to the SD card wasn't anywhere to be seen on my phone. I tried removing and reinserting the SD card, doing a power down and restart. Nothing worked. Before I had a chance to trouble shot the problem, it was working again and I haven't had any problems since. Go figure.