Its true you can't keep dwelling on him and his using, but at the same time you can prepare yourself for his using in the future. Keep telling yourself you can't stop him, you can only control your own actions.
I always would get a feeling ah was going to use. Looking back it would be his behavior. If he was thinking of using he would become more cheerful, he would offer to help out more. Just little things that made me know he was gonna get high in the near future. If you start recording his using, you will start to see a pattern and it could help you.

Last I heard from him, he was trying to sleep it out. The cravings hit him hard yesterday. I have no reason to think anything. So I'll just stop thinking. I am going to keep a journal of his behaviors. Hopefully see a pattern to his drug use. Hopefully, there won't be anymore drug use. But he's an addict and I don't see that as a viable outcome. Stupid addicts always fucking everything up!

Is he going to treatment/meetings?

Sleeping it out? Doesn't sound like a good plan.

He goes to his meetings. He has removed himself from the world right now. He's got no gas and no money. He's in a safe place for the moment. He did stay clean yesterday. He has good days and bad days. Hopefully the good will eventually outnumber the bad. Yesterday he fought his demons and won. Let's see what today will bring. Each day he stays clean is a small victory.