We are an FBA newbie. We have an FBA order that the customer contacted us saying that she did not receive the item. We directed the customer to Amazon’s Customer Service since it’s fulfilled by Amazon. Now, we see that the full refund was issued back to the customer in the Order Details. How do we know whether that particular "Not Received/“missing” item was actually delivered or undeliverable and returned back to our inventory? Or Amazon simply issued the full refund for the “not-received”/“missing” item from our account even if the item was delivered and not returned back to our inventor? Thank you!