I have recently had a similar experience. I posted two items from VIC to two different buyers in NSW on the 17th March, one buyer claimed non-delivery on the 23rd (Estimated delivery was 20th-24th) accusing me of not posting item and demanding refund. I lodged an investigation with Austpost as the other buyers item was delivered (as was another item posted 2 days later to QLD). Buyer was rude and aggressive in their behaviour despite the fact I was attempting to locate the package and resolve the issue for them, and communicating this back to the buyer. The buyer lodged a refund claim via ebay on the 25th, only one day after estimated delivery. I even contacted Ebay Customer support who advised me on the 30th, not to refund until Austpost had completed their investigation (due to the buyers behaviour). The buyer had initially agreed to wait until the Austpost investigation had been completed (I was offering a full refund on completion of the investigation, escalated this claim to ebay customer support on the 31st (Yes today) who have instantly refunded the purchase despite informing me not to until the investigation is completed. Even if Auspost now find that the item has been delivered to the buyer, the buyer has already scammed their payment back and I am out of pocket! Disappointed that Ebay advised me to do one thing then turned around and did the opposite themselves!!