Heinrich's odyssey showed us Tibet through the eyes of a foreign resident taken into the culture, but his real journey was that of personal transformation. This is the stuff stories are made of, and are rarely found in chronological events unless the writer digs really hard to put one together. There are two excellent examples of character transformation in the story. The first is a turning point at which the extremely self-centered Heinrich sees the consequences of his behavior and decides to be different. But people don't really transform in an instant - they just change direction, and even that is shaky.
Personal transformation is a very slow process.
In Tibet, Heinrich undergoes the slow process of personality change. At the end, he not only wants the son that he abandoned, he has modeled the role of father through contact with His Holiness, the Dalai Lama. The loneliness of imprisonment and isolation, and the sharing in the young Dalai Lama's life as the Dalai Lama discovers the world that only the foreigner Heinrich can show him, makes Heinrich aware of his ability and his need to be a father. The turning point scene makes an excellent use of symbols, and could have made more use of them than it did. I can't guess Heinrich's motivation for changing at that moment, but it could have been shown.