Britannica encyclopedia failed to mention the holocaust for a decade so I need to read obscure writings about different camps? Surely they would have written something about the major ones.

Kids don't write in a loose leaf journal, it would be a well protected book so to speak until accidentally lost like Ashley Biden writing about her father showering with her. It's not a diary by Ann Frank, it's a cherry picked conglomerate of literature edited by others using pens invented after her death. It's a story not factual evidence.