What do I do , when they go MIA



So my friend had a relapse after getting 7months on his belt . The first time this happened he checked in with the facility to stay on track and that helped him quite a lot . Now his had another one and he isn’t communicating he doesn’t reply my messages or calls and I honestly even know where to start looking . It’s been 5 days it’s driving me crazy the idea of not knowing is working me up .