ORIGINAL: buzzard bait
Many sellers will not even send overseas for reasons like this. I think he fulfilled his responsibility when he mailed it, and he's doing the right thing by agreeing to send it to you again.
The mail service in your country admitted a mistake and should not hide behind some international agreement that you and the seller cannot possibly know about. I think it's expecting too much of the seller to ask him to navigate that to get his money back. I think you should demand that your postal service make this right.
I also think it's really good of you to ask here instead of just going into a bitter dispute with the seller. I hope all goes well in the end.
Jim
What do you do when the seller (cottage industry business) is in another country and you get a tracking number from his postal service but the package never shows up? I'm having a similar issue, ordered a high performance diesel from Spain a month ago and have nothing to show for it but a tracking number that terminates when the package left Spain 3 weeks ago. All the seller is doing is telling me to check with the USPS. The way I look at it, my responsibility was to pay him for his goods, his responsibility is to get it to me. I don't dictate how he does that so if he chooses a less direct route than Fedex or BBT (Big Brown Truck) that's on him if I have any say.