Talk:List of Collection Items w/Pictures/@comment-47.205.76.178-20200130154301/@comment-30544675-20200130205721

That is not a collection. It is a "one-off" item quest. The quest is called "Opening the Diary." The item is called "Key" but it doesn't go into your inventory, and it is not something that a friend can give you. See this page:  List of One-Off Item Quests

Keep trying. When you get Mill to Pairs mode, use the best luck talisman you can, for example a Diamond Horseshoe, and hire as many Sleuth friends as you can. Good luck.