In my cloud of calorie filled happiness I didn't think to ask why but, here is my conclusion: I walked into Sugarbaby's about 15 minutes to closing time. Maybe they tend to give away cupcakes before shutting down? If so, I must make sure to subject all future birthday cupcake purchases towards closing time so as to extend the joy to people other than the birthday gal (or boy).
By the way, this had only happened to me one other time at Inversion on Montrose. Fran and I came away with a whole bag of pastries that fulfilled my breakfast for an entire week!