How did Mark's words about afterlife become public?

Question

In The Invention of Lying, Mark said these words to his dying mom:

Mark: You're wrong about what happens after you die. It's not an eternity of nothingness.

Mom: huh?

Mark: You go to your favorite place in the whole world.

He said these words in the hospital in presence of doctors. Then how did they become public?

Answer 1

Umm.. Because the doctors spoke with other people, who then spoke with other people?

Don't forget that in this truthful, honest society, there probably isn't a need for confidentiality - everyone's going to tell each other everything anyway.