Similar scenario happened to me.

Your options are likely to be 1) return to AAA with credit for miles flown, 2) bump to flights later or next day and UA will not cover meals/hotel/etc, 3) abandon at your own peril.

In my case, I tried the "trip in vain" argument to get original routing credit. The trip actually was to see a friend for his birthday, but the misconnect due to weather mucked up all the rest of the travel...UA rebooked my next outbound flight to be later than my return flight.

UA refused the ORC request.

If you have nowhere to be, and you're willing to put up with getting bounced around in the system to whichever other flights are available, you still should be able to complete the itin...eventually.