Ok. So the first time I did it I turned the transmitter off and it kicked into RTH mode. Cool. The second time I did it I actually set a mission to go back to land in a field behind my house which is 2 kilometers from where I set the mission. I drove home and it had finished it's mission but my props were still spinning. I switched from auto into manual and then I cut the motors. What usually happens if I setup waypoints and get it to land the motors always cuts automatically. But since I was driving in my car with my transmitter near me still on. it may have lost signal and still carried on with its mission as setup in failsafe in mission planner.