BULLSHIT! the scanners are pre-set to the delivery zip code prior to leaving the post office.
In fact, a carriers whole day is set in those scanners. You don't change the zip during delivery operations. The only exception is Sunday parcel delivery's, but then you only change the zip when/if you move from one zip code into another. It's a huge undertaking and it can't be done accidentally. Then, if you should accidentally scan a package that belongs to another zip code, the scanner goes into an error message.
That was a P/M giving you the sunshine treatment.
As for the package not being delivered, if they can get you a letter, then they can get you your parcel. There is absolutely no reason at all why not. I've delivered live bees, chicks, cremated remains and I can't prove it, but I'm sure a few pounds of pot over the years.
There is a 1-800 customer service # to call and *****. Trust me, that will get a P/M's attention! That complaint goes to a POOM (Post Office Operations Manger) and the old saying about **** going down hill goes into effect. Most importantly these complaints affect the P/M's performance bonus. I wouldn't even hesitate to call.
As for the UPS clerk saying that they fly USPS mail, unless you're in Louisville,Ky I'm calling B/S. USPS contracts cargo space on private air liners. This has been the norm since the dawn of aviation.
You guys can piss and moan until hell wont have it anymore, the USPS isn't going away. UPS and FEDEX can't afford it. Their business models depend on the Post Office. The P/O isn't losing money despite what the news reports. Congress mandates that the P/O pre fund a retirement plan for people who aren't even born yet.
I shall now step off of my soap box!