Checking the boy's pockets turns out to have been justified - he may be using or he may be pushing, quite possibly both. I know practically nothing about drugs, but I have the impression that cocain and heroin powder is passed around in folded foil but pills may also be, in which case they are a distinctly hard lump. You are right to be worried and, in my opinion, he should be confronted. You should take this up with him and ask for an explanation, then probably tell his parents after telling him you will. Drug misuse and addiction is a very serious matter, including drinking of alcohol and leads to major disruption of the lives of next of kin and friends plus (for those who are there) the workplace.