Four years old or not, I really doubt this would show on a test! One second of second hand smoke in your mouth (not lungs even)???
FOr anyone else with a false positive, get it cleared up immediately. Waiting for six months just looks like you are taking some "drying out" time. Which in turn makes you "look" guilty since you did not immediately retest.
The stevens guy, for one is a recruiter. I have heard that most have traits very similar to salesmen. If their lips are moving, they are lying! HEhehehee But seriously, two, I'm sure he has heard "I swear I don't do drugs" by those that fail tests more often than every trucker combined has heard, "I aint got no panties on"