That plant to the right of your snail looks like Java fern windelov, and if thats the case, you need to remove it from your substrate or it will die. You cannot bury the rhizome it needs to be above the substrate attached to rock, driftwood, or free floating.
I don't know about yours, but I had a nerite snail that started doing that one day. A few days later, my RCS had started to pick away at it (it had died). I think it just died from old age. I'd say just keep an eye on it.
Before this all happened, I came into work to find that the nerite had climbed out of the tank and traveled 3ft away before rolling back on it's shell. I thought it was dead, but I decided to put it back in the water just to see, and after an hour or so he was back to normal.