Does tracking show the item has been delivered back to you? Was this a Royal Mail transaction? Ask your Postie where they left the item. It might still be in a safe place around your property, or handed to a household member who has forgotten to tell you ( that's happened to me 🙄 ), or to a neighbour.
End of the day, if the item's tracking shows delivery you will have to refund within that timeframe you've been given. If you don't, the buyer will escalate, eBay will force the refund, and you will have to chase the courier / RM for a refund for a lost item, which may be difficult if tracking shows delivery.
The very real possibility is the item was stolen if left in an unsafe place, in view of thieving eyes !
@jredsull
