Unfortunately,  this happens all the time,  items left in unsafe places for all ' eyes' to view are easy pickings for the unscrupulous!

eBay cannot help you if the seller has tracking to show delivery to your name and address,  either eBay nor the seller can be responsible where a courier leaves an item.

You can try your payment provider,  I've heard on here some have had success with home insurance,  not sure if your courier provider would be interested of the facts and can help, worth a try ?

@telboy19752