I looked over my comment and realized I left a whole mess of unnecessary info in there. Oh well.

If he won't check the post office that's his issue. If you choose to refund him that's up to you, but I would make it a condition that he first has to see what information he can find about lost packages or somesuch.

I know it was only a matter of two days for my buyer to locate and claim their cel once we knew what happened to it.