Hi Anxious, your husband taking opiates again would be like me drinking again or a former smoker having a cigarette. The receptors will wake up and even with the best intentions the addiction will re-establish itself. Your husband may think he'll be safe with you holding the prescribed drugs, but as an addict he may go out and find them elsewhere.
I think the whole scenario poses huge risks for his recovery. One option is for you to write to his specialist and tell him/her that your husband is an addict. That could at least prompt the doctor to ask the question. Doctors often get information from relatives, and although they won't discuss, they will take the information into account.
To go a bit further, you might actually tell your husband what you've done. He may be mad, but his past behaviour and the fact that he's been doing so well lately, means the stakes are high for you. It's something to consider anyway.