I'm so sorry to hear that! We were next door at Dovetail (for Critical Lass) when I saw this. Just really stinks. Was it locked to that rack across from Begyle?
Here's the standard advice... I'll post it on FB, Twitter.
Things to do:
File a police report using 311.
Register with Chicago Stolen Bike Registry
Tell as many people as you can.
Print flyers and distribute them to bike shops.
Check the Bike Sellers groups on facebook.
Check Swap-O-Rama and Maxwell St. Market.
Set up a google alert to alert you if someone lists the bike on craigslist or elsewhere.
Set up a new e-mail account that forwards to one of your established accounts to use for communications about the bike.