How can you tell if a used car should have come with a key fab?

I bought a 2003 Ford Escape and the door only unlocks from the driver's side. There's no other way of getting into the car. Should it have come with a key fab? Can I just get a new one and program it?

Fob… Key fob… Not fab. If the door doesn't unlock with the key, there's a problem bigger than the lack of a fob.

If it STARTS you have a chip in the key that the car is programed to accept.
What you are calling a FAB, should be called FOB, in is actually a REMOTE for power locks. A new remote can be used, but you may need someone with special equipment to pair the remote to the vehicle.