Some players report having their friend hop in the vehicle, drive it, then return it to them. Apparently there is a player specific attribute that makes the vehicle do this.
This bug is a result of the hotfix attempting to remedy the coasting vehicles bug from .59 initial stable release.
This is a game breaker.
EDIT: Another player can get into the vehicle to unlock it for original player.
EDIT2: Removing all tires, holding the last tire, relogging, putting one tire on, driving vehicle 1 meter, then putting all tires back on fixed the stuck vehicle as well.