C.S.I. Its Plagued my life!

Upon returning home from taking Mom to work this morning I walked in through the garage only to see the front door wide open. I have no idea how it happened. Steven swears he locked it before going to bed. But how was it opened from a deadbolt? It makes no sense to me! C.S.I has trained my brain to how, why, and whats going to happen next. So as I sit here studying my head is running case after case of all the things that could be happening from a door being left open. Every sound gives me goose bumps! Its quite funny. Until I figure it out or forget about it. Its going to be a long day.