Well, I finally gave up. I called the post office and told the nice lady there of my plight. She's going to send in a work order and have the lock changed on my mailbox and give me some new keys. It may take a few days, but the mail carrier is very nice about handing me my mail if I happen to catch her at the box.
Now you just watch. Those keys will turn up the day after I get my new mailbox key.
Shalom
Oh, yes, the PO isn't altruistic about this. It's going to cost me $15. And I still have to get a new lock for my front door.