I found my assigned title on the master list, but the book “Figures in the Mane-Mist” is either very esoteric or a typo, because I can’t find any information about it. I tried to connect to the discord for more info, but that link is invalid and does not connect to a server.

Those are fake titles made to look similar to names of the books from Appendix N. You are free to imagine what this story would have been if it was actually written and use it for your adventure, but there is no actual book and you don't need to read anything. 

Yeah, I made up all the titles to save you from copyright infringement (and having to read a book lol).

Not sure why I discord link wasn't working for you, I switched it out so it may work now. If not I'll check with the folks running to server to see if they need to generate one.