Another data point for comparison:
Returned CDG-IAD and my bags never showed up on the IAD belt. So I waited to the last minute, said a Hail Mary, left for my IAD-DEN connection and went through screening bag-less. Subsequently transferred to DEN-RNO -did not have time to check any belts.
To my surprise, at RNO, out came my bags and home I went.
Not exactly the same issue as the OP, as I did not "leave" my bags; but interesting (to me) never the less, since as far as I know my bags were never screened.