The past can never be recreated, it is over, people change, relationships change, some dissolve, it is all part of life, part of the growing process.
He has moved on, he has a new companion/friend.
Why are you afraid to be alone? What is holding you back from going out and making new friends, a new best buddy? Possibly there is some deeper rooted problem that may need to be addressed. I don't have any answers, just questions.
I have learned that I need to be the person who understands me....better than anyone else....with that understanding I can continue to grow and enhance my well being.