That blows. I don't know you personally but I would bet that you probably could have a few tokes here and there (off the job of course) and still perform your duties as a RN. Of course, life doesn't work like that and it's reefer madness when it comes to nursing and MJ. I mean I'd rather take a stoned nurse than a drunk nurse, but you catch my drift... If your RN license means anything to you, then you'll go through the hell that most of us here on going through.
Side question though, you said "MJ use without disclosure", meaning that if you had disclosed that you were smoking medical marijuana they would have let you slide? And what led to you being drug tested in the first place?