When you buy FSD and sell the car, the FSD stays with the car.
This is a muddy situation where car was sold back to Tesla, dealer bought it from Tesla and sold to a third party.
Dealer claims it bought the car with FSD from Tesla. Tesla claims the car never had FSD and it was enabled by mistake.
Someone is lying but it's a one off situation.
You don't loose $7k feature when you sell the car, it stays with the car.