Refund on first scan - lost parcel. Who raise a claim?

Hi all

A UK customer has asked to return an item they bought from us (SFP not FBA). Amazon issued a refund on “first scan”. However, the item seems to have been lost by Royal Mail (it’s been over 2 weeks it is showing in transit).

We opened a Safe-T claim to say that the item wasn’t returned to us but posted by the customer. Amazon denied it with the following reason:

Blockquote

We have denied your reimbursement request for order 203-6xxxxxxxxxx.

Why is this happening?
The buyer returned the merchandise to you using the carrier Royal Mail and tracking xxxxx715343GB .
If a shipment is lost or damaged in transit and you would like to request a reimbursement, you must raise a claim directly with the carrier.

Blockquote

It doesn’t make sense to us because we aren’t the one providing the label (Amazon is!) and using our business account to raise claims, we would have to give information about how it was posted, how much the postage cost (the regular questions we answer when we put claims through for our usual customers).

We challenge the decision but they just denied it again saying we need to raise a claim.

I am at loss at what to do given they provided the postage label and should be putting the claim through

Has anyone got the same situation?

Thanks for input!