Curious whether the "time out" was the therapist's idea or something you and your son agreed to try independent of the therapist? Doesn't sound like a bad idea, but I'm wondering if the no-communication period will be for a few weeks or months?
Did the therapist offer to help you mend the rift?
Your situation reminds me of what's gone on between my wife's brother and her father. Her brother, Dan, has been diagnosed as bipolar. He has drug and alcohol issues on top of that -- bad enough on its own, an even worse combination. He cut himself off from the entire family for a few years. Then he gradually re-established mail and phone contact with my wife their mom. He held off on contacting their father (separated from their mother since they were kids). Their dad was crushed when Dan shut down in the first place but felt even worse when Dan reconnected with others but continued to keep their dad at bay. There was no explanation and, knowing how tenuous relations are with Dan, none of us want to pry as to Dan's reasons for keeping the dad out of his life. That said, my wife has gently mentioned how their father is deeply hurt by the lack of communication with Dan.
Unfortunately some of what Dan has sought is financial support, we suspect it's for fueling his drug and alcohol habit. The mother has helped out with small amounts of money. Some of it gets paid back, some of it remains promised to be returned.
Anyway, I've seen the effects first hand and it's tough.
Hopefully, after some time to reflect, you and your son can bridge the differences between you. It likely won't happen without more hurt and heartache, but maybe you can get there with some work. In the meantime, let those emotions wash over you and, yeah, find solace in the support of other family and friends, including those here at the DU.
Best wishes.