"I had it last in my trunk, which is where I looked for it. It wasn't there, and my books were out of order. Which means someone was rifling through them. And Libra wouldn't tell the house elves to do anything. Dad told her not to."
Which, often, was as effective as speaking to a brick wall. Sometimes he wondered if Libra really did forget everything she was told, or if she knew perfectly well that she could get away with murder if she just cried a little.