Where do you live? Are you getting a lot of cold weather especially if this cold snowy weather isn't a normal situation for your area.


Also how old is your door and the door frame?


This might sound crazy but it happened in a place where my wife and I first live. The door and the frame where old and wooden and living in Pennsylvania we tend to have cold weather as well as humid hot summers. Over the years the weather causes a strain on some older doors and they will shrink in cold and expand in hot humid weather.

One night it was really cold and I went to work and as I always do I lock her in the house (meaning locking the front door) She called me 2 hours later telling me that the door was popping open. The door was lock but yet door was just popping open. She got her coat on and took the keys with he just in case but she went outside and closed the door than she pushed on the door. It came open without the key.

Long story short the wood had shrunk so the lock wasn't fitting into place right.

You may have very well locked the door but with some of the crazy weather this country could be having could cause your door to mis function and that is why your door was open.

Just a thought.