One chest is not so bad. There are only 5 chests in each location and checking where they are is not such a big deal to be honest. Not trying to argue with you or anything, but when Triumph dropped the only thing that I had left was to beat Skolas... And that was an entirely different matter altogether... The game basically tells you in which patrol you are missing the chest, then you just gotta go figure it out. Even if you look for it without looking online, I don't think it takes more than a couple of hours. Again, this is not meant to make a fool of you, but to encourage you that it could be worse!