Philip Pullman's already been cited... Narnia, too, to an extent, uses it, in that the wardrobe refuses to work as a doorway for certain characters as they grow older - I think the Professor in The Lion, The Witch and the Wardrobe says he's tried in the past after being able to get into Narnia, but never had it work again. Or something. They remember, at least, what it was like. (Except Susan, who becomes too grown up to remember it properly.)

Mmm. Narnia did spring to mind, but as you say only Susan really counts as an amnesiac, and the strong implication is that she only forgot because she didn't really want to remember.