I'm sorry you are going through this. Many times I hunted down my son on the street, and each time we ended up going for a meal and coffee, then he went back to the street because he was not ready for help.
He has been missing, lost in his addiction, for 8 years now. Some people ask me why I don't go look for him, and my answer is always "and if I find him, then what?" I don't want a front row seat to his addictive lifestyle. If/when he gets clean, he knows how to contact me and I am certain he would.
So for now, I begin my days with a prayer asking God to take care of him and to do for him what I cannot. Then I live my life well, as life is meant to be lived, and I live in faith instead of fear. I spent too many years in that dark abyss of fear and I refuse to go back there ever again. My faith is my light and it sees me through each day.
I will keep your brother in my prayers too, that one day soon he will choose a better path.
Hugs