There is eBay protection for an item that is not delivered. That doesn’t equate to eBay protection for an item that’s delivered and is subsequently not able to be found.
There is consumer protection when a purchased item from a registered Australian business isn’t delivered. Again, that doesn’t mean protection for an item gone missing after delivery.
Your card issuer will protect you in a case of non delivery - but you’re dead in the water if the item was delivered and subsequently went missing.
PayPal Buyer Protection - ditto.
It’s the same thing as though your car were stolen 3 weeks after you’d purchased it. The seller would have no responsibility in that case!
Australia Post has no responsibility for the missing item - unless they were negligent or it was their courier who stole the item. Even if you think they were negligent in leaving the item, good luck in proving it. If your seller had included additional insurance, that doesn’t include insurance against post-delivery theft. What made you think that it does…?
You need to mitigate your risks. If theft is a problem in your area, there are options - security camera of some sort, parcel locker, work address delivery, etc.
Your seller clearly has proof of delivery - tracking status shows it was delivered. In that case, opening an INR case is futile. (INR = Item Not Received.) The case would close as soon as seller provides the tracking number which would prove delivery.
From what your opening post says, you opened a SNAD / INAD case. (Significantly Not As Described / Item Not As Described.) Wrong case type. Of course you can’t return an item that you don’t have. Therefore - as you yourself say - you’re now required to post back a faulty or wrong item.
But there’s no case/dispute type that is applicable for you, because as I’ve said, eBay doesn’t offer protection against items that go missing after a successful delivery. Like it or not, your item was successfully delivered according to the tracking.
Really, your only hope is for you to contact Australia Post. How do you know it was indeed delivered? Did the courier photograph it? Is there a signature you don’t recognise? If there was a photo, can you ask for it to be emailed and do you recognise the background?
Your only remedy would be if there’s doubt it was actually delivered. Failing that, if you’re right and it was stolen by an unknown person after it was delivered, you’ve no recourse except to find the thief and get back the item or its value from him/her.
