Let's cut to the chase: I loaded an old save to get the Oblivion Walker Achievement (finally) that had successfully completed the Impatience of a Saint quest and had Saint Jiub's Opus in the inventory. Fast forward 3 Daedric artifacts later, I look in my inventory and notice that all but page 6 of the Opus are in there! Since there is magically no more book, I look to my quest log; no mention of Impatience of a Saint anywhere.

Has anyone had this happen before, or am I going crazy?