If the hermit wants the shell, it will have the shell, unfortunately.
Have you tried checking after lights out for a few hours?
If not I would venture to say the slug didn't make it. Like said, they aren't very hardy creatures.
Hopefully it's just hiding from you.
Live in the Western MD/West Virginia/DC Metro Area?
Join our very active regional forum Here
Like the advice someone just gave you? Add to their reputation! Click on the balance icon underneath their username and let them know.