Bike was locked to a bike rack in front of my office building and a restaurant at the ground level near Wacker and Madison. I came out around 5pm and found the rack empty. As I stood there holding my helmet, a woman came up and asked if my bike was locked up there. She said they were having drinks at the restaurant and saw someone in a hoodie come up and start sawing at the lock. Sparks were flying apparently. Someone from their group called the police, but they didn't show up in time or at all. Two people approached the thief and asked if he was stealing the bike, he said yes and carried on. She said it took a few minutes and then he climbed on and rode north on Wacker. No one from the restaurant knew anything.