Huh. Sorry I wasn't there to help out. =\
If you're quick, I think you only really need two or three local people to deal with it. One admin keeps the interloper blocked, a second admin undoes any blocks by the interloper, and a third user goes running to the stewards ASAP. Depending how many people are available, more can watch the interloper's deletion and protection logs, reverting as needed -- one quick person per log seems the way to go, avoids confusion and keeps them outnumbered.
That at least seems like it might work? The problem would be getting those people together and organized on very short notice.
But then, I've never dealt with this sort of thing on that sort of scale, so... -Luna