I'll add that's it's always a gamble when making decisions in situations like this and it's easy to second guess yourself and beat yourself up over it. But the chick may have been unthrifty and would have died no matter what you did, even if it seemed well.
Sometimes the chicks will wander out of the nest at night. It's rare, but I've had it happen. Also, sometimes the hen will accept the chick under her but attack it once it's in sight. I've had both things happen before.
I would put it back in the nest box when the mother is sitting in there. She will warm and it will dry. It is the same age as the others so it should be fine.