It's also possible to miss that star stone by going about the quest in a certain order. (without breaking into her house)
By the time I went adventuring outside the town in beta I had come across 2 star stones. (1 in the murder room, 1 with Evelyn) This playthrough I did things in a different order and she was gone when I went to see her. No second star stone. Hopefully there's a point where you'll come across it later, when you catch her maybe. Or maybe a way to cheat your game into giving you the effect of the second stone. Don't want to start over...
