He may have became stressed out from all the activities. And he also could be very tired from it too. When A dog is stressed they can't eat .
Leave food and water down for him. How long has it been since he ate? He is at a good weight, which is a relief. Is he peeing and pooping?
Was it hot outside where you went? If so, he could have gotten heat exhaustion.
Give him a little time to bounce back.
