https://motherboard.vice.com/en_us/article/8xkvgb/facebook-promises-not-to-secretly-delete-more-of-zuckerbergs-messages-for-now

Old Facebook messages sent by CEO Mark Zuckerberg and other executives were deleted from recipients’ inboxes by the company, Techcrunch revealed last night. People who had corresponded with Zuckerberg, as far back as 2010, confirmed to Techcrunch that his chats have since been removed, while theirs remain.

Zuckerberg’s messages “no longer appear in their Facebook chat logs or in the files available from Facebook’s Download Your Information tool,” Techcrunch wrote.