Not USPS as I live in New Zealand, but I did have my company's courier provider once state about missing scans "Don't worry about it, we are just not very good at scanning stuff".
This was during the height of the pandemic when packages were taking weeks to travel around New Zealand and everything was chaos. Given some of these packages contained tens of thousands of dollars worth of product, when they were not scanned in anywhere, sometimes for over a week, I did worry — quite a bit!
So, I can feel your pain. Hopefully some tracking pops up soon.