You gave the wrong instruction to that person, they should not themselves send the item to the correct address.
Send another message explaining when they receive the item to open a case for item not as described. you will then pay for the return postage, for the item to be returned back to you.
You then need to post the item to the correct buyer.
Keep the tracking safe for the resent item, you will be able to use it should a case for item not received be opened, and that tracking shows delivery, it will close the case in your favour.
@saddlebagsmosaic