Need help with an A to Z

Haven’t had an A to Z in a while and I need some help on how to appeal. Here are the details: On 11/28, I purchased a label for an item through Amazon and shipped the package. On December 9, the buyer filed a “Package Did Not Arrive” A to Z. The tracking shows that it was out for delivery on 11/30, but it never got updated after that. Today I received notification that Amazon has found in favor of the buyer and that the amount will be deducted from my account and count against my ODR. Since I purchased the label through Amazon and the tracking shows that the item was received by UPS, shouldn’t Amazon be picking up the cost of the item and not have this count against me?