I had one of those too a few weeks ago. In my case it was a package that was 'held' at the post office. My assumption was that the buyer had to pay tariffs and did not bother or want to and basically just abandoned the package. After 3 weeks the status changed to 'vacant', which according to the USPS means the person no longer lives there. I never had it confirmed that the buyer had to pay tariffs or the fact that he didn't was the reason for the status change to 'vacant', that was just my theory.
Anyway about 10 days later the package landed back at my doorstep but there were no tracking updates on the USPS website....it just appeared.
