"The defective part was loose and missing the magnesium powder used to ignite the propellant that shoots someone to safety, Roberts said."
From that I take it only a very small amount of powder was missing. It would take someone with superhuman powers to say if a few grams of powder were present or not in a component that weighs a few kilos - give or take?
I strongly suspect the method of discovery was not "God-dang it Bert, this seems a mighty load lighter than it should be".