You need a lawyer familiar with wrongful termination cases. You at the very least have a right to review youremployee file and rebutt the charges against you. I would go get a hair folicle test at your own expense and go to a lawyer.
At face value (and I really good at sniffing out addict behavior. It takes one to know one) You're story doesn't jibe with addict behavior. I could be wrong - Nurses usually get caught when their addiction causes them to get sloppy. But for now I would pursue your legal options quickly - the longer you wait the harder it will be to prove your case.
Hppy