Yes, it is normal in those circumstances for the patient to be working on detox and recovery, not calling people on the phone. Many rehabs don't allow phone calls for the first several days, others don't allow them at all. His job is to concentrate on himself and learning how to live a sober life.
Your concern is quite common, but he is there for HIM. While he's away, you could use the time to work on your own recovery. Find some al-anon meetings for yourself. They can be a tremendous help.