The drivers have a lot of packages to deliver each day. If they stopped to ring the bell and wait to see if anyone was home at every stop, they wouldn't get done until late in the evening. So they often drop and run, if it seems safe to do so, because it's faster. Would I like that to change the few times I am home and they deliver? Sure. But am I willing to pay a lot more for shipping? Not really. So I understand it, and accept it.
I have a note always posted on my front door asking all delivery persons to leave packages in a secure location behind a locked gate. They all are very good about honoring that request. Recently in the few cases where I was home (a rare occurrence during delivery hours), I took off my standard note and put up a special note asking them to knock - they all honored it.
Most of these guys want to do the best job they can, but also want to get home to their families at a reasonable hour. Taking a few simple steps can help them make you happier.
Reading a note and following what that note said takes almost as long as ringing a doorbell and waiting a moment!
Our UPS man will put the box on the porch and ring the bell before walking back to the truck. The first time he did it I thought I just wasn't fast enough to the door. Then I figured out it was to let me know he had been there.
I was waiting for something to be delivered once. I had a third floor apartment, and my kitchen sink window looked out over the parking lot. I'd been clicking Refresh all day on the computer in between doing other things. As I washed dishes, I saw the UPS truck drive up and stop in the driveway (big apartment complex, nowhere for him to park) and turn on his emergency blinkers. I saw the truck moving around, as though he had gone in the back and was moving, getting packages. I watched and washed dishes and watched...and then the blinkers turned off and he drove away. NEVER got out of the vehicle.
I went to my door, looked out, nothing. I hit Refresh until I got a message that a tag was left, no one was home. Oh NO no no no.
I called UPS, and in our area then I could eventually get to the distribution office, and I got to a person and I described the situation. And that was when I discovered that the local center is open until 9 for after hour pickups. I was annoyed to have to go out, but at least they were open late enough for DH to get home to be with baby-DS...
At least everyone is getting their packages. I'm still waiting for 2 packages from UPS, one from 2009 and the other from this past July. The July package made it to my local warehouse and then nothing was ever updated on the UPS site beyond it arrived. I called UPS and was told because it was an
Amazon order I would have to contact them to contact UPS.

Sure I might as well call my 3rd grade teacher and get her involved too.

By the end of everything UPS did nothing and Amazon refunded my money plus an extra credit for my trouble. Amazon had never heard of anything so crazy as them having to contact UPS because they were the sender before either.
I'm mystified by the amazon rep.
There's nothing at all that YOU can do. And the normal thing that UPS does, doing some backtracking thing (that they charge for), isn't appropriate for amazon. Amazon has their own UPS CS reps to call to get a bit more info, and ultimately it's not the CS reps who do a single thing with shipments marked as lost. I don't even know who deals with them, but it's NOT customer service. CS reps at amazon do NOTHING but replace the package or refund you. And that's it. And that's the way it is supposed to go.
So I don't know what the amazon rep was talking about, but what happened with you is absolutely positively what happens with amazon shipments. Nothing out of the ordinary. Maybe it was the rep's first month there or something?
Have you ever checked the tracking information for it, by the way? When I was an amazon CS rep, I kept a file of tracking numbers. And comments by customers, the normal UPS reps that the customers got to talk to (omg the things out of their mouths...they had NO clue of the contract of their company with mine), and the specialized reps that WE dealt with. I would check on things every so often. Packages that disappeared months before, suddenly getting delivered. Packages appearing elsewhere. Packages getting left behind bushes in the summer and reported as lost because the customer had checked "everywhere, I swear, everywhere!" being found in late fall back behind the roots of the bushes when there were no leaves left to hide the package....
But really, UPS told ya true there, and the amazon rep was the one who was wrong in their statements. The reps replace the package, mark it with the correct code so the correct department is notified of it, and that's it.
This is very common. It is more efficient for UPS to pay the Postal Service to deliver packages in rural areas than to do it themselves. The only problem in our area is that it takes UPS a while to hand over the packages.
The hybrid shipment IS common. But it's known when it happens, and the tracking info makes that obvious. Sounds like maybe this particular package was erroneously delivered to USPS, perhaps in a "switcheroo" for another package where it was meant to happen, and since there was no USPS delivery confirmation number connected with it, USPS had no clue what should happen with it.