Special Service Campaign 40D didn't fix it

I had a major malfunction error indicator several thousand miles ago, and after two visits to the dealer, they finally realized there was a Special Service Campaign on my 04 Prius -- SSC 40D. They downloaded all new software for the car and sent me on my way. Now, the same malfunction happened, only this time the car rolled to a stop in an intersection, and could not be started. The dealer said that they had "forgotten to reset the ECU" when they did the service campaign before. The car is now running again.

I can't tell if this is plausible explanation, or if they just rebooted something and crossed their fingers. Can someone shed some light on what might be happening?

Thanks.