Day-Tripper..... I am sure you aren't being serious. FYI... when I was a 2LT I had a TSSCI and they literally sent people to talk with my high school friends in person and asked questions about me. They asked my friends all sorts of questions about my parents, me in high school, who else I hung around with etc....
You're probably right about the background investigation being far more stringent for Service Academy appointments, but I don't think it's quite as thorough for ROTC selection. My son (whom eventually did not follow through with ROTC, due to injuries suffered in an auto wreck - relax, he's fine now) had what I would a rather perfunctory background check, at best.
Of course, none of his neighbors or teachers or employers ever knew if he'd smoked pot or not, but he didn't have a reputation as a stoner. He was just a clean cut, polite young man who got good grades, performed well at sports, was on time for work & was seen mowing the lawn & shoveling snow from time -to-time. And his friends were straight up guys, who'd never rat him out as trying anything not legal, as most real friends are.
Given the sheer size of ROTC, which I believe is 10,000 - 15,000 at any given time nationwide, the ability to determine if someone has ever used pot or not seems a difficult task. Of course, once you're in the system, never use again as you will be under the spotlight. But the same goes for underage (under 21) drinking, which I'm almost certain is subject to as widespread disregard as it is within the general college student population (if not to the same extreme).
And from second hand sources I believe that recruiters for enlisted ranks are more than willing to overlook a potential recruit's juvenile indiscretions. Sometimes outright lying (not saying this is the norm, though). But tell me it's not typical for a recruiter to say something along the lines of "You've never used illegal drugs at all, have you?"
I'm shouldn't make recommendations and I'm not trying to encourage lying. Sometimes I guess I write off the cuff without more forethought.