I have gone flawless in Trials of Osiris, gone to the Lighthouse, gotten the drops from the chest, and have not gotten the Grimoire titled "The Lighthouse", which I proceeded to do a search on. It does indeed "drop" from going flawless. I went flawless in Year Two only, this might be the issue. Edit: I'm reading about five posts down...I went flawless week one. I did it right when it was bugged, didn't I...