I suppose you must not know chemistry. Ammonium sulfide is not what McVeigh used in his bomb. He used potassium nitrate.
Also, meth is not made from ammonium sulfide. It is made from ephedra, red phosphorus, and iodine. That's all. Sure, most manufacturers don't have access to pure chemicals so they have to extract it from things like cold pills and starter fluid, but ammonium sulfide doesn't figure into it.
Ammonium sulfide is a chemical commonly used to make stinkbombs, because it smells very strongly of farts or rotten eggs. A single ampule is probably enough for one.
Your neighbor's kid is not going to blow anything up, it's just a harmless practical joke. Chances are, he knows how to make the stuff, too, so don't bother confiscating it because he'll just make more anyway.
I think you replied to the wrong person