I grew up in the 60’s and 70’s and so been there, done that. My parents were clueless about drugs. I would bust my grandson all the time. Come home late and hit the refrig “Oh I see we have the munchies...”, or “You are a little too bit chipper and talkative for 2am...”, or “What’s up with the camel routine?”.
All tell tale signs of doing something. Of course you have to have multiple indicators...
And you have know the person’s baseline characteristics. Out of ordinary is when you look deeper...
What does that mean?