Unfortunately, the animal control officer doesn't work weekends or holidays. He came and got it this morning - by which time the little guy had died. He was active yesterday morning when we went out for groceries. I'm sure he got dehydrated; I just couldn't think of a way to get him water while in the trap, and wasn't about to let him out of it.
The garage is, hopefully, squirrel-proofed now. We put hardware cloth over every opening we could find. I don't want to do that to another squirrel.