Mail her a card, a letter or something. Nothing real deep, just a little line letting her know that you're thinking of her. Try also to call her and ask her out for dinner, a "girls" night out.
By the way, you haven't lost your daughter. She isn't lost if you know where she is. She is with her dad, albeit he sounds like a Disneyland dad, but that will backfire. I know, I've been there.
