Bryan Alvarez reports that there were two scrips for Night of Champions and one of them included Roman Reigns not wrestling. This is before he had to be rushed to the hospital. So that could mean that there were already plans in place to have Dean Ambrose wrestle Seth Rollins tomorrow night instead of Reigns. That might also explain why they gave away the Reigns vs. Rollins match on Raw this past Monday night.
The writing crew is redoing three days of television (tomorrow, Raw, and Smackdown) and they have to get that done within 24 hours.