Rabbit Hopped Out

One of the bunnies, Pawlette Bunny, hopped into the car and stowed away with the human today while she went to physical therapy. What makes this worrisome is the fact that the human's therapy place has a swimming pool. The rabbit was in her swimming suit, and I'm sure she amused herself diving into the water while the human was being worked on. Does anyone know how I can keep these bunnies from sneaking off for extra dips? I believe that there is a charge to use the pool and I don't want to get a bill for bunny swimming in a few weeks.