This does not compute. What does what you have in your pockets have to do with a drug screen? (which, I personally feel is an afront to the 4th ammendment), also, what does your having a weapon, or not, have to do with a drug screen? That is bull.
I have had to take that test before too, never had a problem with anything in my pockets, or my carry. What you have in your pockets cannot neutralize what is in the sample....makes no sense.