One thing is certain - the burden of proof isn't on ME (or whomever) to show that they DID send bitcoins. The burden of proof is on the VICTIM to prove that they never received goods. As Bitcoins are untraceable to an IP, and a digital good that has no static owner....
....You get the point.
As far as I'm concerned, you got your bitcoins. Prove that you didn't.
He has proved that he sent you a specific address to send the bitcoin to. Unless there is a transaction confirmed by the network for the amount of bitcoin that you owe him to the address he gave you then he has proven that you did not give him the bitcoin as agreed.