I sell on eBay, and hate it when something like this happens. ---->
|I would call eBay in person on the phone so that they can pull up the whole transaction and see what has transpired. They could tell you what to do in this case, and then it would be in the eBay records and you won't have to worry about having done something that would make the buyer blame you. I'm guessing they would tell you to mail it to the address on record, and then it's up to the buyer to retrieve it from his workplace (if that's why he had the address changed). That's just my opinion. Best wishes for an easy fix.