Yes the leaver must`ve been accidently moved, it happened to me once.
Regarding the valet key, I don`t think Mazda has one, I only got two keys when I bought my car and they are both full keys that will open all locks and start the car. I think this feature is for locking your belongings in the trunk when you visit a questionable neighbourhood, or when you park say in an airport. This way even if someone breakes in your car, they will have no way of opening the trunk, provided you also locked the rear seats so that they can`t be tilted.