SCAMMER! sent an EMPTY package.

I sold an expensive handbag, and the buyer was not happy - so I approved the retrun process and offered a complete refund when I got the handbag back. The customer purchased a 500g tracked Australia Post satchel which arrived EMPTY!!! The buyer got a full refund from PAYPAL. What Can I do?! For a start the handbag weighed 700gms and would not fit in the dimentions of a 500gm stachel.