Yesterday I flagged a "moved to chat" comment on this answer as the chat it links to gave a page not found error. To my surprise the flag was declined as apparently the chat works fine for others. I am logged in (tried logging out and back in actually) on chat but still getting page not found. Is there another requirement to view old chats that I may be missing?
According to this Meta.SE post you need 10k reputation to view frozen/deleted rooms. It looks like neither you, nor any of the other users that can't see this room have at least 10k reputation on any site so you wouldn't be able to see it.