My friend, you do not know that he is not triggered by everyday events. You don't know whether he misses you or thinks of you. You don't know how he is able to move on or if he is able to move on at all.
Someone actively using their drug of choice is not going to be feeling a whole heck of lot, and if they are, they're going to be doing all they can to mask those feelings with that DOC.
Those of us feeling our emotions in raw form have to find healthy ways to work through them. Reaching out to others as you have here is a good start.
I cried at home, in the car, in restaurant bathrooms, and sometimes standing in the grocery aisle. It happens without warning and as times goes on it happens less and less.
You will get through this, I know you will. One step at a time, one day at a time.
Hugs,
Alice