In the chapter called The Dementor, (in my book it's on page 79) when Malfoy comes in it gives brief explanation of who he is. It says "Draco Malfoy and Harry had been enemies ever since they had met on their very first train journey to Hogwarts." But they didn't meet on the train, they met in Madam Malkin's robe shop! Maybe in Britain to meet someone is to know their name, but I think this is a slip up.