We went to the post office and talked to the manager- apparently the US post office has tracking numbers that they do not usually make public.
They showed it to us, and it says it was delivered.
BTW, I was born in the United States.
I'm purely joking above, never implied anything. But I don't understand what you are saying - that the passport is sent to you by regular mail and the post office has a record at your end of what was sent and that it was delivered to you? It's possible they can access the scanning code from each piece of mail and know the sender and addressee, but that sounds unusual to me that they are verifying individual mail. Also, does anyone know are passports sent out regular mail?