Complex sentence: When the Baudelaires examining Lulu's tent and Violet found her ribbon, she thought that Olaf must kept it in the previous book, but however earlier in the book in Chapter 2, she wore it and put in her pocket.
Split into simpler sentences: When the Baudelaires examined Lulu's tent and Violet found her ribbon, she thought that Olaf must have kept it in the previous book. However, earlier in the book in Chapter 2, she wore it and put in her pocket.