@belmont-ink-toner wrote:
should I be worried?
No, in fact the buyer's actions are likely to backfire on them.
In Australia, a buyer is not eligible for Buyer Protection if the seller provides proof of postage (I presume you have this with the courier service you used). Delivery / receipt is irrelevant, so if they refuse delivery it's quite likely they will lose the dispute and have no item.
Obviously, if you receive the item back, I would recommend refunding the buyer their payment, but less all costs incurred to send it etc (that would be eBay, PayPal and courier costs).
