USPS or Assurant lost my Trade in

Sent my ole iPhone in for Trade in back in January and just got notified my trade in was canceled. Filed a claim with USPS but Assurant didn't insure the package. It got lost in Louisville, TX where it appears a lot of others have been lost as well. What has anyone done to get this resolved? Hard to swallow pill that I am out money over a mistake/issue that isn't due to me.