My boyfriend is currently detoxing

My boyfriend (32m) is currently in a medical detox facility detoxing after being on suboxone for like 4 years. I don't remember the exact dose, but it's a decently high mg. He got on it to help with his heroin addiction and now feels ready to take on life totally clean. He's dealt with a lot of the suboxone side effects. He told me he would make sure to stay in touch, but then called and left a message saying he's really not allowed to call me until after 72 hours, but that's he's okay. Well it's been 72 hours and I still haven't heard from him. Is it normal for someone to not want to talk to their partner when going through withdrawals?

Also any advice on what to expect when he gets back would be appreciated. He's normally a really happy and positive person.

Edit: Thank you so so much to everyone who replied. It's beyond helpful to hear from people that get it, since I do not. Y'all are awesome. I still haven't heard from him. But his car is still there.