Do you have a dog door? I've been able to get through a dog door to get into my house. I even raised the door thing from the outside. It's pretty disturbing and we'll probably fix it soon.
No dog door. But I do have a very friendly mutt that is kept in the den/kitchen part of the house while we are out. I am presuming this is what kept the burglars out of that part of the house. She can bark pretty well.