Very strange situation, but certainly some lessons to be learned here like signature required to confirm delivery for anything of value. More communication between seller and buyer confirming all information would help.
First and foremost it is the Buyers responsibility to confirm correct shipping address in PayPal, AG, Amazon, or any other payment/delivery system. I confirm my shipping address is correct for every Amazon purchase. Stuff happens when complex computer systems with human interaction are involved.
Would be nice self protection if the Seller confirmed Buyers shipping address, but not required. If the item was shipped to the address provided by the Buyer to AG or PayPal, then the Buyer has to resolve with the shipping organization - NOT the Seller.
If you buy from a business that ships UPS or FedEx, you deal with them regarding delivery problems. Only for the sake of goodwill does a business offer a refund due to a shipping company screw up. Did the delivery service happen to take a picture of the item left at the destination address?
For future reference, Proof of Delivery cuts both ways. Both parties benefit from requiring a delivery confirmation signature.