Yep not much you can do if the USPS says it was delivered even if you can provide some insight they wont do diddly.
I got a new mailman in the beginning of November, I received mail for another house, same number next cul de sac down for two days. I took the mail over there and dropped it off. Come to find out, my insurance renewal bill, exxon cc bill, car payment on another car etc. I did not receive. I asked the other house they denied receiving anything, contacted Post office they say it was delivered explained how I got their mail for 2 days, they said talk to them. Long story short late on 6 bills. This is in a subdivision of homes valued at 800K+. I truly believe their little s@#t bag kid just threw it out, he a little PITA in the neighborhood. Moral of story nobody cares about anyone else anymore.