Trusting, I do understand how you feel. He may be engaged now, but who is to say that it will last? Let's pray that the tides of change will hit him and he'll come to realize that marrying the ow will not be the answer to his search for "bliss".
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.