I was two streets from my home base, and right after clearing an infestation. I was driving Suv and was backing up; the screen turned upside down, and I was suddenly on foot, with a hoard of zombies in front of me. I exited the game and it returned me home. I checked my map and it showed the vehicle still there. I went to it, no vehicle, waypoint set and all. Now I have no vehicle, and none nearby. I am in The Wall mission.