A girl smiles at me and I can't get her out of my head?

I'm used to getting smiles at work, I'm a polite guy; however, this girl came in last night and blew me away with her smile. I haven't seen a girl smile like that ever. She was very beautiful too.

I always ask customers if they need any help, and that's when she smiled. I wanted to talk to her more. It all happened so fast, and just seeing her smile made my night perfect. Now I'm hoping to see her again. If I do see her again what should I say?