He did see her when she was Chantarelle. I think there are a few things keeping him from remembering her when he sees her as Anne.
1. It was a very passing interaction; only lasted a couple of seconds.
2. He was distracted from worrying about Buffy and didn't really look at her.
3. He dismissed her as a silly child and didn't really look at her.
4. She was in LOTS of makeup and a fancy dress as Chantarelle, and dressed normally with lots less makeup as Anne.
5. She wasn't pouting as much as Anne (I'd say she's finally happy).
6. He's generally self-centered, so unless you make a big impression, he's not going to pay much attention to you and remember you later.
That's my take.