I answered Yay in the poll above but only because a contract already exists by default, doesn't it. As long as one keeps the evidence (original advert, communications, proof of payment, proof of sending/delivery, etc.) then that is surely all that is needed to realistically and practicably go to court should it become necessary (assuming that one also has the real name and address of the other person in the transaction).
The kind of scam that you experienced would not have been prevented or your problems alleviated if you had had a formal written contract with the scammer.
So the question is: What would a formal written contract offer over and above what we already have?