Hi i am too currently working at a drug/alcohol treatment center too, and thats extremely ridiculous your boss even brings that up in a staff meeting. I know a few fellow staff members that have got surgery and have been perscribed pain medication (and was given morphine at the hospital),and we all wish them quick recovery, there is no shame in having to take prescribed medication.
I recently got a tooth pulled and first time ever, have I told the truth that I am in recovery(to a health care professional), dentist was cool about it, and I was cool to get the ib proph 800s.
Back on topic, not everyone who works at the facility I work at is in recovery, some of my coworkers in the administration building arnt 'one of us' and it was told by the ceo of the program that those people can drink responsible. (They arnt the type of people that will brag about drinking a few beers anyway).
I'd bring up why is it any of their damn business why I should even tell them that I am on any morphine/type medication, seems like your employers HR needs to really look into that.