Amazon rejecting reimbursement because my inventory was in a 3P warehouse

Amazon lost £5,000 worth of my inventory during the fulfillment center process. I tried to file a claim, but they rejected it with several excuses, all of which I’ve proven to be invalid. Now, their final excuse is that we sent our products to a third-party warehouse, but the issue is, we shipped everything to the location they instructed us to. Can they really do this? Any thoughts or advice would be appreciated. Wishing good earnings to everyone!