eBay will believe the carrier rather than the buyer (or seller). If the online tracking report for the tracking number shows delivery to the same zipcode (5 digit) as what the buyer gave for the shipping address, it will presume it is to that shipping address. That presumption is rebuttable by documentation from the carrier that it was not delivered to that address (the document does not have to give the actual address but merely state it was delivered elsewhere than [your shipping address] since there might be privacy issues). This covers errors by the carrier in mis-delivery (the carrier can tell this by matching the GPS coordinates of the delivery scan with the facts on the ground) and a scamming seller who sends a low value package to another address in your zipcode. See here about appealing the decision if the carrier can document such a problem: https://www.ebay.com/help/buying/returns-refunds/appeal-ebays-decision-return-missing-item-buyers?id...
On the other hand, neither eBay nor the seller is responsible for the theft or other disappearance of the package from your porch, doorstep, or other place at your address. You can try your homeowners or renters insurance agent to see if that would be covered at what deductible.
