User blog comment:Master Sima Yi/Assassinews 03-03-'13 — Assassin's Creed IV: Black Flag trailer and screenshots/@comment-4999424-20130312204140/@comment-4829046-20130313043842

Here is a comment from someone

"Because this mission isn't in the game, it's either made up or part of the Tyranny of King Washington. I've looked, it's not part of the single-player."

Strange though. I think I remember this mission and the dialogue.