User blog comment:Seieireppa/Nanako’s Magical☆Mystery☆Adventure, part 4/@comment-25977712-20150317114452/@comment-25977712-20150317130231

If you look closely at the sentence " blah blah blah I took the liberty of locking the door with my personal master key so as to prevent anyone else from disturbing the scene… of course, blah blah blah"  This could mean Sakaki did something after locking the room up.