So I was right. It has been lost. Early in the linked page it says: "The idea of divinization, of redeemed human nature somehow participating in the very life of God, is found to a surprising extent throughout Christian history, although it is practically unknown to the majority of Christians (and even many theologians) in the West. In Orthodox theology, however, it is the controlling doctrine."
You had mentioned that the Mennonite/Amish might know this?
" You had mentioned that the Mennonite/Amish might know this?"
Me? I'm sure if I did I was kidding!
I must say it is astonishing to me that that as recently as the 19th century Anglican hierarchs understood and preached Theosis. Think for a moment on what effect that belief, regularly preached and believed, might have on a church!