LUKE: So, back from the ball, huh?
LORELAI: Yes, I left behind a glass slipper and a business card in case the prince is really dumb.
Yet another Cinderella reference. In the fairy tale, Cinderella loses the glass slipper at the ball by which the prince, through a laborious and long-winded process, eventually manages to track her down. Lorelai suggests leaving a business card might have led to quicker results.
Is Lorelai’s response supposed to be a hint to Luke, or just a comment on the stupidity of Christopher? Either way, it feels as if Luke’s opening gambit is his way of testing to see if Christopher is going to be sticking around or not.