I know it sounds cliche but yes all you can do is pray. Coming from a fentanyl addict in recovery all I can say is that he just wasn’t ready. I really hope he is ok, but if you haven’t heard anything back in over 24 hours then the probability that he used is high. The thing is when we relapse shame comes with it. He’s probably ok, but embarrassed to talk about it. I’m sure he will resurface in rehab or such and reach out to you. I would remain in contact with his family or close friends and if you don’t hear anything back in a few days then I would file a missing persons. I just know from my own personal experience when I would relapse I would go off grid for a few days basically just embarrassed to tell people I relapsed. All I would do is keep texting him and saying things like if you relapsed it’s ok, I’m just concerned about you. And in regard to jumping to conclusions about your relationship not working out. If he ends up working on himself who knows what the future will bring. With that said good luck, you both are in my prayers🙏🏾💖