USPS is the worst.
I overnighted a substantial bank check yesterday to a seller here with a guaranteed 3pm delivery today. Not only did the check not show up today, the system only shows a record of it leaving my local sorting facility yesterday, with no record of any kind of acceptance to the destination PO.
It was an hour wait time on the phone to even speak with a human... and they told me they will need a day or two to sort it out and find it, but I can be "assured" they will refund my money for the overnight charge, as if that makes anything better!
Meanwhile I'm facing a 90 day hold on the funds of my original bank check if it doesn't show up, and of course will need to pay for the replacement check on top of that.
Lesson learned, do NOT use USPS. EVER. It's an absolute disgrace.