Sister, they are far more resourceful than we moms give them credit for.
They can find drugs in any city in the world, they can find places to stay when we worry about them sleeping under bridges and they have been places far scarier than a homeless shelter.
It's hard to let them go, but thinking we have any control is only an illusion. He is learning that there are consequences to his action and he knows what he has to do to get back in. If he wants it bad enough, he'll find a way and of he doesn't, maybe it just isn't his time yet.
My heart and prayers go out for you, it's no picnic being us (or him) and things will work out exactly the way they are supposed to right now.
Hugs from one mama to another.