When I worked at Dominos, there was something of an incline to the parking lot. My boss pulled in one day and parked his car and came in, and we were in the back room just shooting the [censored], waiting to come on shift, when one of the other guys working came out and said "Hey dude, your car's rolling away". We always joked around with each other, so my boss just said, "Yeah, sure" and kept talking to me. The guy was insistent, so my boss finally got up and looked, and sure enough, his car had rolled across the street into this grass lot that gradually sloped downhill. He went sprinting out across the road and got the car just before the decline got really bad and brought it back into the lot, making sure to set his parking brake this time.