I have a friend in the Army National Guard who swears by this stuff. After he came back from his first tour of duty in Iraq he was smoking with us like the world was going to end.
He had a job interview and drug test coming up working as a security guard and he says he bought himself a bottle of Strip from GNC and his piss test came back clean.
But then again he is a pretty small guy. About 5'8, 150 pounds and because of the Army he stays pretty active. Weed most likely doesnt stay in him too long because of his amount of physical activity and very small percent of body fat in him.
I doubt you passed because of the drink. Most likely dilution or it just doesnt stay in you too long.