No, I m not contesting that he didn't have to declare what he got.. but I'm annoyed to the possibility that he might be put on a list that going to give him hard time everytime he goes through customs.
Yes, his passport is probably flagged now.
If he is flagged, he now has 50/50 odds of being pulled into secondary inspection whenever entering Canada regardless if he has anything to declare.
There is a possibility that the slate may be wiped clean when he gets to 18 but I doubt that. The only way to tell if you have been flagged is to travel. The only way to get out of being flagged is to continue business as normal and eventually the secondary inspections will go away.