[MRM]

I don't think there is anything you could have done. Also, given the timeline you related, I don't think you would have made the connection at ORD. You likely would have raced to find the door closed with the plane still at the gate or just pulling away. They wouldn't have held the flight for you. Based on your timeline it seems likely you would have gotten to the gate maybe before the plane took off but not before they closed the door to prepare for takeoff. And as any traveler knows, once the door is closed it doesn't open again. You might have made it, but the chances are slim and weren't worth the risk of being stranded in Chicago. Frankly, turning around and starting over is exactly what I would have done.

The only thing I see you might have been able to do differently is to have checked your app to see if the flight was delayed earlier in the day. IF it was showing delayed earlier and IF you had enough advanced notice you MIGHT have been able to reroute before the surge of displaced passengers. Otherwise, if you had your laptop with you at the airport you could have logged into your account on United's web site and seen if you could find an alternative routing. But really, I think you did as well as you could have. When there isn't a plane there just isn't a plane and no amount of arguing with the agents will get one for you if none are available.