As was mentioned upstream, a check of the 'Track my bags" on the UA app will probably solve 90% of the issue, at least getting accurate information.
Their tracking has never let me down.
Last week I checked 2 small bags from IAD to MSP. When I arrived at MSP, one came out, but after the second didnt show, a quick check of the app showed it was enroute SFO.
I stopped by the baggage office, gave them my info, and they said they would deliver it.
I watched on the app as it was reloaded on an SFO-MSP flight later that day. Tracked the flight and headed to the airport (20 minutes away) as it landed. Mine was the 2nd bag out, I grabbed it and stopped by the baggage office, thanked them for their help but that I had my bag so they could close the case.
All of that was just with the info in "Track my bags". As an aside, of the few times I have needed to go to the baggage office, it always surprises me they dont seem to want to use the same info we have...
Also, for those curious, I checked those bags at Dulles, and the one to SFO was scanned "loaded with override" 12 minutes later. I was kinda surprised at how fast they got it there, considering the baggage drop area was kind of a madhouse.