I have heard of an Indian-Tibetan tradition that a great saint, Issa, an avatar or essence of the creator, came from a humble home in Palestine and spent several years in Nepal and Tibet, healing the sick, preaching righteousness, hanging out with the poor, contradicting the teachings of the Brahmins and other authorities, narrowly escaping prosecution several times. Eventually he went back to Palestine. It's a story that so neatly fits the lost years and Jesus of the Bible that It's almost too good. The Tibetans were great record keepers but their monasteries and scrolls have been destroyed by the Chinese. I don't feel it is irreligious to think He would have put in some of those years preaching to the lost sheep.