Thank you all for your help, I have never flown lie flat before so I certainly don't want to get bumped from it if it is still operating! I'll wait for tomorrow given the schedule update that was referenced.
Some more details that may end up being helpful - the flight I had booked was ANC-EWR-DCA. The EWR-DCA leg had been in the mid-morning; however, I now see it's gone and the only possible EWR-DCA connection for me is at 2:00 PM (ANC-EWR arrives at 7:40 AM). So, it could be stopover issue and the system re-routed me after my connection was cancelled into DCA. But, I also searched for ANC-EWR-IAD (which I would happily do) and that also did not show up, despite an 8:20 EWR-IAD flight. Would UA prevent me from booking a 40 minute connection time? Last but not least, I searched for just ANC-EWR, since I would just hop on Amtrak to DC if it meant I could keep my lie-flat, and that route DID appear - with an upcharge. I'll try to get a supervisor first but worst comes to worst, that would still be worth it to me.
Edit: Now I see this 8:20 EWR-IAD flight has no open seats in First. Would that prevent the route from being shown as available to me? I would again happily take an Economy Plus seat on that leg if I got to fly the ANC-EWR.