Why didn't Wilcox die in the explosion?

Wilcox was warned about the danger to his life and had left his home with his family..... taking them with him.

But alas that work so well organized and boldly carried out should all have gone for nothing! Warned by the fate of the various victims, and knowing that he was marked down for destruction, Chester Wilcox had moved himself and his family only the day before to some safer and less known quarters, where a guard of police should watch over them. It was an empty house which had been torn down by the gunpowder, and the grim old colour sergeant of the war was still teaching discipline to the miners of Iron Dike.