That is totally incorrect, under Australian law, the sale occurred in QLD , the contract of sale occurred in QLD, where the parcel went is irrelevant to jurisdiction. Furthermore, eBay Australia is the intermediary in this line contract where they act like an escrow service and hold the buyers fund and do not release to you until the time there is proof of delivery. Again, under law, delivery occurs at the post office it was lodged at https://www.legislation.qld.gov.au/view/html/inforce/current/act-1896-006#sec.34 . QCAT will hear the matter and make a determination