I had parked the vehicle in grocery store lot. I had been shopping for 20-30 minutes when I was called to the service desk and was told to go to the parking lot. My car had rolled back across the parking lot aisle and had hit another vehicle. I verified that the car was in park. No one was in the vehicle at the time. It just slipped out of park and rolled. I called Ford Motor Company and they are not going to do anything about it, even though this is a documented problem they have had, just not on my particular year and model combination. They are the ones who suggested I file this report.