If you have a snail that's been in its' shell for 4 days What is wrong?

If it's still tight up in its shell, I mean no flesh is showing, and the operculum is all you see, then it's still alive ( it takes muscle tension to stay this way) if not I would take it out and poke it a few times and see if it retracts further, if not smell it if it stinks real bad, it's dead.