I track 'em if they're high value. I custom-made mod shipped to me this summer that I'm really glad I did track it. The day it was supposed to arrive, it turned up "Undeliverable as addressed" in the system. Now I know the vendor had my address right, 'cause I'm a repeat customer of his. So late that afternoon, I went to the local post office with the tracking and some whiskey, tango, foxtrot questions. The supervisor spent some time in the back and found my package for me. Turns out it had been mis-sorted onto the wrong route/truck that morning. That driver then fat-fingered the wrong status into the system and it was going to be returned to the sender.
Same thing happened to me last week. The local post office told me it was a "covering" carrier as my regular carrier was on vacation. The excuse the "covering" worker gave was "no mailbox".
Lucky they still had it in the back like in your case.