Top secret clearance question?

My friend, in the AF DEP, got a job that requires TS Clearance. At 1 point, for about 5.5 months, a little more, he was feeling "no" I am not going, and was pretty certain. He smoke pot once to see what it was like, and that is it. By the time he goes back to MEPS he'll be 6mo clean and at the very least 8mo clean by the time of clearance procedures. If he tells this story, will he be discharged? Btw, he doesn't want to tell his recruiter, so he wanted me to ask here.