Did you go to your local Postal Outlet or Post Office, and enquire about the parcel?
It's probably too late now and it has been returned to the seller. But ask anyway.
Contact the seller and ask to be notified when the parcel arrives back with him. Then the two of you can decide on next steps.
Which is why I hope both of you were polite and professional during the time of the dispute. If things stayed friendly, if tense, there can be a final resolution.
You may get the item after all, but it would be no surprise if the seller wants you to pay for the postage to complete the transaction.