To quote from the article
> Thus the consequences of this incident appeared to be less grave than in two earlier cases—in Brazil in 1987, and in Thailand in 2000—when unsuspecting scavengers who dismantled old radiotherapy machines exposed themselves and their families to very high doses of radiation. Four of the exposed people died in Brazil, and three in Thailand, and more were seriously injured. The cost of cleanup and recovery for their communities was substantial.
> Officials, especially in the United States, were relieved that the stolen Mexican capsule did not end up with terrorists, who could have used it to build a “dirty bomb.” Even though many planning scenarios predict that such a bomb would probably cause few radiation-related deaths, its economic impact could be disastrous.
Two previous incidents of material disappearing killed the thieves, and even still a dirty bomb isn't any more dangerous than a regular bomb to the intended victims. They're essentially not really a thing as I posted earlier. You'd probably just bake yourself trying to build one.