Ah, kayakers have the same issue. A car up at put-in, one at take out, and keys are supposed to stay on the vehicle. I'm a bit paranoid about hiding my key on the car every time I leave it, because you never know who's watching. I end up just taking my keys with me. That's great, until I get in a situation where I'm stuck in the river somewhere, and the other person needs my keys to the car. I need to get a permanent key hidden somewhere, so that everyone I paddle with knows where it is, but it'll only get put in that location when I'm in my garage, or something. That way, it's there for emergency, but I'm using my regular key most of the time. Bummer about the stolen car, of course.