Could you please tell me if a customer returns an item using a label purchased from eBay if it is marked as delivered but it is not actually delivered, with no proof, how do we go from here?

The original seller can not input a claim as the label was purchased from ebays Royal Mail account and any compensation would be given to eBay, also unless eBay are willing to give account number and address a claim can not be opened, but eBay are taking delivered on Royal Mail website as enough proof, even if the post person have marked it incorrectly.

I have had the issue a few times and each time it has resulted in hours of being passed pillar to post between agents who don't have a clue. I'd like a standard across board for any future issues.