When Miss Price gets her witch's broom, there is a letter attached to it. She looks at it for a moment, then puts it aside. If you look closely enough when she still has it, there is absolutly nothing on the paper!
Well she is a witch. Perhaps the paper is supposed to be blank and only people with magical powers (witches) can read it. I know it is far fetched, but a possibility. It's probably really a slip-up, I just felt the need to be confrontational :)
I'm the one who posted that slip-up. As I recently discovered, on a television screen, the paper looks blank because plain and simply, TV (at least the one I saw it on) quality isn't good enough to show fine details like that, but on a DVD displayed on a computer screen, you can see the print.