We went. No sign of any mice for the first 4 nights over Easter then when the rest of the caravan park packed up to go home the mice moved in in droves. I don't think they got into the camper at all but sitting out at night there were dozens running in & out of the annexe. They didn't bother me too much until the morning we were packing up & I found one in my suitcase! 
Hope you ditched the hitch-hiker and ruined its travel plans.
Kids would have wanted to keep it too maybe?
Or did you invoke Darwin's law of natural selection?
By teaching it to swim or give it a real bad concussion.