If there is upgrade inventory (R) at time of checkin, and you are Elite (any level), you get it.

I suspect there was an open R seat released just before the time of your co-worker's checkin. If that was released and EUA did not run to properly allocate the seats, it would be available to the next Elite who checked in. Your coworker lucked out.

Either that, or your name/OnePass number wasn't right so the computer wasn't processing you correctly.