the hempseed oil is a very good argument. i heard from an english teacher, that a bunch of people were falsely testing positive for THC. This was in Arizona.. they all had in common one thing; they used the same brand of hemp lotion. they all got off the hook.

in most urine drug tests, it is possible to measure how much THC Is in your body. this helps them determine how long it's been since you have smoked. if you've been clean for 30 days, you are probably only testing positive for trace amounts of THC--which is why they're most likely buying your story. had you smoked a blunt the previous day, the THC ppm (parts per million) would be way up there; an obvious sign that you've either been smoking, or using a hell of a lot of hemp lotion

best of luck to you.