For what it's worth, I think that you may not have been notified because you booked through a work related Travel Agency. It is possible the notification went to them rather than to you. I book revenue tickets and sometimes it's easier to book a new ticket for my new plan and then cancel the old one for a travel credit. Within mere minutes of doing the new booking I get notified of the double booking - and am given a short window to cancel one or the other before the system does it for me.