Why does USPS show item as delivered if package is nowhere to be found?

I am assuming you ordered through amazon? If so just call Amazon's customer service tell them you never received it and ask if they can resend.

I've never had an issue doing that the couple of times this happened ..probably was delivered to wrong address.

I had that happen twice the past year. One time, the package came the next day, maybe the postman clicked it as delivered when it was not. The second time it went to somebody else's house, my postman is known to make mistakes,
and whoever got it put it on my doorstep two days later.

So much depends on the particular delivery ...I do usually wait a couple of days and then call or email. I believe when you go online it will say to wait a couple of days and then report it.

In my situation when I got a notification stating my package arrived even ones I had delivered to someone else ....they never arrived a couple of days later. I've called or emailed and had them resend..in one case it was a gift basket to a friend...they had run out of them so I chose another to send, Amazon gave me a credit for the other....then like a week or two later it arrived...not sure what happened to it but my friend got a bonus.

Another time we ordered a Santa outfit for my dog. It was supposed to arrive several days before Christmas end ended up with a delay notification on the day it bc was supposed to arrive...and so I had the option to cancel which I did. About a month later it arrived..what the heck?

One thing I do like about Amazon is they are good about refunding or resending your package if it does not arrive even if you are notified it had. Not sure if it is because I am a good customer, don't abuse this and am always kind and respectful to the customer reps.

I once got a notice my package was being delivered today, it was delivered the day before the notice

Yeah that happened too!

Its like yeah thanks!

Intervention of a third party, the guy who stole your package.

Mistaken information, your delivery chimp very gently placed it on the wrong step.