Hi there,
I'm so sorry for what you are going through. I can understand that you're worried. The Methadone program works for some addicts, but research has shown, just like in your case, that many of those entering the program either sell their Methadone on the street to get something else instead*( their drug of choice), or they begin combining methadone with other drugs and their addiction spirals. My AH wasn't in the programme but he bought methadone off the street which he combined with suboxone and cocaine. What I've learnt is that methadone can be really dangerous in combination with other drugs. In my AH's case the combination of methadone and subs was lethal. He OD'ed and died last summer and the medical examiner told me it was because he had combined methadone with suboxone at a high dosage.
I don't know what to advice you considering whether to report the doctor or not, but I know I would have considered the fact. But that is the only thing you can do, if you choose to do it. The addict has to be willing to quit drugs and work towards sobriety himself/herself. We cannot do anything to change/push that. My AH wasn't willing to work on his sobriety even though he got clean and the outcome was devastating. I hope the other members on SR can give you some more advice on how to go about with the doctor's issue.
Sending you blessings and hope //SoDev