Most students know little about the drug scene because, obviously, they don't do drugs (or are just playing innocent). Either way, that's basically how it is on campus- you are unaware of the drug scene if you aren't a part of it. Drugs aren't in your face, and it's rare to even see marijuana, or smell it for that matter, at parties. Alcohol is the drug of choice among OU's majority, and while hard drugs are no doubt on campus, they're not floating around.
Basically, when it comes to drugs on campus, if you want some, you probably can find them somewhat easily. But the good thing is that those who aren't into the drug scene are rarely, if ever, affected by it. There's no pressure put on students to do anything they don't want to do. And sometimes it seems downright hard to find the things you do want to do. But as with any college campus, it's there if you look hard enough.