That is about as stupid as they come. I can understand not allowing a child sugar in any form only in situations where it is medically necessary. And many breath mints contain sorbitol or xylitol, both of which are sugar alcohols and not metabolized like real sugar (they are more complex carbohydrates).
This does not sound like a medical condition that makes total avoidance of sugar a necessity. It sounds more like someone depriving a child of anything that smacks of fun. In all likelihood, the breath mint (which he is not going to find in the yard) is the tip of the iceberg. I strongly suspect that he is not allowed to listen to any music except the 225 pieces of Kingdumb Sxxx. I bet that anything that remotely resembles fun at school is strictly forbidden, and this humanoid will go after the school to make sure there is nothing fun going on. All time off is spent in field circus. There is zero tolerance for irregularities at boasting sessions. No TV. No outdoor sports of any kind. No nothing.
And what would that witless be doing looking for a breath mint on your front lawn? More likely, it is in the trash can of someone else, or he swallowed it. And since when would you expect the empty package to end up on the lawn? The last I knew, the pockets would be the first place to look, and then the trash can. If it is a Tic Tac, there might be no evidence whatsoever (and especially if it was the first few out of the pack, with the remainder of the pack still in place). Even if the Tic Tac were on the lawn, it would be like looking for a needle in a haystack--those things are quite tiny, and (especially the white ones) look amazingly like pebbles or seeds.
Besides, I wonder if it ever occurred to him that skulking on someone else's lawn at 3 in the morning looking for a Tic Tac would get someone in the area to call the cops to report a suspected burglary.