Here's what Ron and Misty say about the lock, dunlurken:
VAN SUSTEREN: Ronald, I understand that there does not appear to be any forced entry into the home in that back door. So how do you think it got open?
CUMMINGS: I honestly don't have any clue. I don't have any clue. Somebody, maybe a locksmith, picklock artist, I do not know. But it was definitely locked, and somebody came in through it. So I cannot explain it.
VAN SUSTEREN: Misty, let me ask you this same question. Misty, how do you think that door got open?
CROSLIN: Someone had either picked the lock, they would have had to pick the lock. That is the only way that anybody could have gotten in our back door is if they picked the lock.
http://www.foxnews.com/story/0,2933,492185,00.html