With USPS anything is possible. I mailed a package where I generated the label on my computer and then dropped the package in the box at my local PO kiosk. The only tracking info that would show was the same, that USPS was still waiting for me to drop off the package even though it was in their hands. There was no record of any intermediate steps on route until luckily the package was logged in as having been left on the porch of the recipient.
The PO I mailed from is a substation in a Supermarket. I try to avoid the regular postal outlets after several episodes of them arguing with me about rates, usually trying to run up the charge. I don't get that hassle from where I mail. I doubt they'd be able to help on this.
It occurs to me maybe I transposed the # when entering it on my seller page. I cannot locate the receipt. Nice. I think the buyer got it. I'd be hearing by now if not. I'll just put it to the back burner and hope..