exactly right - the note was written first - it was supposed to be a kidnapping, but it went bad.
on the flipside - if the killer was someone in the household, then the note was staged simply as a diversion to make people believe someone else was inside the house. how do you make a convincing false claim that a stranger was inside your house? you say "look, they left a note". what else can you do to stage that?
I think we were both right last night...I hope I'm proven wrong.