During the Tea party scene, after their (Mad Hatter, Alice, and March Hare) "clean cup move down" thing, Alice tries to tell her story of Dinah. As you can see, Alice is sitting in between the March Hare (on her left) and the Mad Hatter (on her right).

When the March Hare suddenly says, "I have an excellent idea! Let's change the subject!" and hits the Mad Hatter, Alice who's supposed to be in between them disappears.