The passenger can unlock the doors and keep the fob in his pocket.

The driver who has no fob can start and drive the car, drop the passenger off along the way, ignore the chimes and "key not detected" warning, continue to park the car elsewhere and shut down the car normally.

The hitch is, the car can't be locked without a fob nor can it be re-stared by anyone without one.

When the passenger with the fob catches up to the car, it can be re-started normally.