Wow, that really sucks on a couple of levels. It's frustrating to have a false positive and have to claim otherwise, and the possibility of someone lacing your buds... that's a definite abuse of the dealer relationship. If that's the case, I am sorry to hear it.

In regards for testing for contamination from other drugs, someone suggested soaking in water. JUst so no one goes and waterlogs their buds: soaking them in water neither determines if they are laced nor does it remove contamination!