By that logic you could walk into Walmart, purchase an item, head for the door and then Walmart would ask you to give that item back because someone else wanted it. Naturally ANYONE would refuse. Walmart would then call the police and they would take the paid item from you and haul you out of the store.
Here's a better example ...
1. You go to a car dealership, sign a contract to purchase a car, put down a deposit on the vehicle with the VIN# ABC-123.
2. The dealer agrees that the car will be prepped and ready for you to pick it up a week later.
3. You show up a week later, only to find that the dealer has sold the car to someone else, and it's sitting out there in the parking lot waiting to be picked up. Maybe another buyer offered more money. Maybe the owner of the dealership sold it to a golfing buddy.
4. The dealer offers you a similar car with the VIN# XYZ-789. But you are adamant that this isn't good enough, and you have a binding contract in your hand.
If this were to happen you'd have plenty of recourse. You'd be entitled to your money back, either in cash or as a credit for another purchase. Maybe the contract contained a provision that said the dealer has to give you a full refund plus an extra $500 for your trouble. Whatever it is, you're either leaving the dealership made whole or you have plenty of legal avenues you can pursue.
One option you absolutely do not have is to climb behind the wheel of car #ABC-123 in the parking lot and tell the dealership staff that you're not leaving unless they give you the keys and let you drive the car away.
The management of the dealership will call the police to deal with you, and the police will deal with you as they see fit -- even if they have to drag your ass out of the car and injure you in the process.
Dr. Dao learned that he wasn't going to be driving the car off the lot that day.