Problem with Foreign Buyer and Post Office

I sold a game on ebay, and shipped it out with a couple other games. The post office marked all the items I shipped out that day as delivered to the zip code of the post office, with no further tracking available. I called up the post office, they said it was an error, everything will arrive fine. Couple days after I ship, the buyer of GTA opens a case because he thought I shipped his item to the wrong place because of the messed up tracking. I told him what the post office said. I found out he was using a courier to ship it outside the US. I messaged him about a week later, asking if he got the game. He didn't respond. I've sent him several messages over the past couple weeks, no response. The case was opened on Jun 05, so it will close soon. My question is, what can I do to not have the case count against my seller rating. I'd be fine with refunding the buyer, but all the other games got to their destinations, and this buyer is not communicating. Ebay wants me to respond to the case with either verifying the tracking number, saying I shipped it without tracking, or issuing a full refund. I have the paypal printed receipt showing that I shipped it to the right address.