I was wondering if he could be doing that but he's even in the exact same position. I may have to pull out a webcam and record over night to see if he does indeed move. It's so strange. I don't think there's a surplus of food there, especially after 4 days of him not moving.
I'm starting to wonder if maybe the tiny anemone that my Pom Pom Crab is holding may have gotten him. I noticed the Crab was hanging out under an outcropping that the snail is near. Maybe he got a little zap on his foot? I wouldn't think it would do so much damage to cause him to recoil for days, though if indeed this is the case.
Thank you everyone so far for your input! It's definitely helping me keep my sanity on this matter XD