Answer: Ten Kabbalists, the authors of The Book of Zohar, wrote in a cave called Idra Raba, which exists until this very day.
According to The Book of Zohar, one of the authors spoke, another explained and clarified, and a third wrote down what was said. They had no disagreements because they were as one single desire, one single soul. They described all the possible states of all the individual souls that ascend and connect into one soul called Man, Adam, in a hundred of volumes.
The Book of Zohar was concealed for a long time and was discovered by chance. Its pages were found in a market. It turned out that they were used to wrap different food products. Whatever was found became accessible to the public. The attempt to find the other volumes did not yield the desired results. In the middle of the 1940’s, The Book of Zohar was revealed by Baal HaSulam, and he began to write his commentary on it.
This is a very special book considering its origin and its fate, in the vicissitudes of the people associated with it, and with what happened to the people who had it because there was only one copy of The Book.
2,000 years have passed since it was written, and still anything associated with The Book of Zohar is yet to be explored: where are its hidden parts and what happened to them. We are yet to discover all that and to explain it. I am sure that everything will be revealed with time.
From the Kabbalah Lesson in Russian 2/5/17