Ya see, one of the better ways to tell when 564 is close to striking is that precognitives and precognitive stuff starts messing up - like normal precog-precog cancelling, but on a much larger scale. It tends to only work an hour or so ahead of time, but a warning's a warning.
And, this time, the detectors had gone ping, Los Angeles was in lockdown and the air-raid sirens were going, and then...
564 doesn't turn up. Everyone breathes a sigh of relief.
And then everyone starts panicking, because 564 isn't meant to do that.