I just found out USPS marked one of my items as delivered but I never received it.
I had this happen with an Amazon order a couple of years ago. There is a street address almost the same as mine, but differs by one letter. I went to the annex where the carrier works out of. Item marked as delivered on a Saturday, but I sat watching TV in a room with the window having a clean shot at the mailbox--nothing was delivered.
The carrier said they delivered it, I pointed out the other address, and her boss directed her to go to the other address. The carrier said she went to the other address to make sure she hadn't mis-delivered, but that resident said the carrier never came--carrier was reprimanded and pulled from delivering mail.
I then called Amazon and they re-shipped the entire order with overnight delivery. I wasn't expecting them to do anything, really, and they went well beyond satisfying me as a customer with a purchase history. I've now had +10 years of mis-deliveries. Started because of the one-letter difference, but now the address can be quite different--carriers can no longer see, read, or deliver.