I think it's an ill fitting lid, and she figured out how to get around it. The lid is weighed down pretty good, like, 75 lbs worth of books good. And she still got out. I don't want to run out and spend another $20 on a lid if I can resolve the problem myself. Even my boyfriend thought about using small bungees to pull the lid down, but if there is a gap, it won't do any good to push from the outside.