I was in LAS on Thursday morning and saw UA 914 to IAD and CDG on the departure monitors.. thought they had perhaps changed flight numbers for the LAS-IAD flights, but when I saw the 777 sitting at a gate realized that it had been a diversion. So, I'm not sure if someone COULD have gotten on, but at least the airport info system and the gate were both set-up to show it as a LAS-IAD flight.