My car key is an electronic fob. When I get to the trailhead I disable the fob by taking out the battery and tape the fob to an underside of an engine hose. The battery in the spare tire cavity. In the future I'm going to start leaving all the paper work at home....I rarely get stopped by authorities, and am going to assume that most would understand my motivations. The entrance combination code gets written inside of my pack, with a sharpie. On the trail I carry about three 20's' drivers lic., and one c.c.