Any tips on how to get money back from Item not returned but refunded

So a customer sent an item back via Evri via Amazon and as per Amazon’s procedures they refunded on the first scan.

Problem is courier returned the item to the customer (as per the tracking and the fact I never received it)

I raised a Safe-T claim and they told me to talk to the courier, the courier won’t talk to me as it has been ‘delivered’ (it has just back to the customer) and are not helping any more.

Any ideas?