Suicidal mousies at that.
Thursday evening last week I came home -- was going to be going to a con, so Friday morning was the last time I'd be there until Sunday night -- and I looked into the trap. Didn't see anybody there, but I saw almost a shadow of movement -- so I drove it out to the park. Beautiful dark grey. Not very smart. Didn't want to leave the trap. Wasn't very quiet once it did.
This week -- didn't see anything Tuesday night. Didn't see anything Wednesday morning. Wednesday evening I didn't really see anything, but the nothing seemed to be strange, so I brought it out to the park. The hiding mouse was still alive at that point -- but I don't know whether it was clinging to the trap out of terror, or if it had been there for a long time, hiding well enough that I couldn't see it, and was dehydrated. I finally got it to let go of the trap, but it didn't move away from the spot it was in.
These traps have a large "room" which I can look though -- there is a mesh on both of the ends, so if it is occupied, I can see a shadow when I look though one end at the other. The mouse entrances are opposite each other off to one side, and I cannot see that area there. the only place to hide would be underneath the area where one or the other entrance sits. And now 2 mice within a week have hidden exactly there. Odd. None of my prior captives have done that.