I have soooo much experience with this crap.
If you're in the US, I've had packages say "Delivered" only to have them dropped off a day or two later.
I kinda think it's because the mail person didn't want to get out of the truck and I have to wait until a more diligent mail person is on the route (I have 3 different mail people).
Sometimes I'll catch a neighbor on the cameras placing the box at my door because it was misdelivered.
Other times, I'd forget that it was being delivered by USPS and they will shove whatever they can into the mailbox, while I've been sitting there all day, waiting for the doorbell to ring and it to be dropped off at the door.
You can try calling your local post office. I've been lucky enough to have them physically check the truck when the mail person returns from their route. At least twice, the package was still there.
One time, a manager drove to the post office where the package was being held (under the pretense that they tried to deliver it and I wasn't home) and delivered it himself in his pickup truck.
It can be a tedious process, but when you call, they assign you a case number and 90% of the time, a real person calls you back. They have ways of tracking packages outside of just the note that says "Delivered."
