When he was a kid, yes. I think the experiments they were performing on him and the countless of other kids were supposed to greatly improve their reaction speed to superhuman levels. However, since the drug they used proved to be highly unstable, they had to stop. Thayer was thought to be dead.
They explained this in the School Festival arc, when he fought the only other guy who survived the experiments, that guy who worked for the military. I think he was supposed to bring Thayer back or something, but as we all know failed to do so because Thayer was simply more awesome.