Nicole Richie  signed autographs Saturday during an appearance in Chicago on behalf of her Winter Kate line. Her travels to promote her latest collection have taken her all across the country , northward to Canada , and even to Europe . While Nicole was away, Joel was on daddy duty in LA including a trip to the mall with Harlow that inspired a heartfelt blog post  about working hard to provide for his family. On Saturday evening he had to take off for a DJ gig in Las Vegas . Nicole, meanwhile, had some excitement in Illinois — she evidently ran into John Mayer  outside her hotel, and was surprised to see how tall he is in person .