MTS-escape artists?

Generally a lot of MTS up at the water line means something has gone wrong with water quality. They can be a good warning system.

I concur with psyche if it is a lot of snails at or above the water line something might be wrong with the water quality or they are starving and looking for alternate food. If your tank is planted though it is probably not food but water that is the suspect... might want to check it.
 
I never seen MTS crawl out but I have seen primarily pond snails who would go above the water line also would crawl out of the tank to their doom. I seen this happen in my assassin snail tank, the MTS don't care but you always see pond snails above the water line outside of the water.
 
AquariaCentral.com