Rose threw the object late during overtime in the Pistons' 117-110 loss to the New Orleans Pelicans on Monday.
After Pelicans forward Nicolo Melli drained a long two with 38.2 seconds left, a visibly upset Rose walked over to Detroit's bench during a timeout and grabbed a pen laying atop a clipboard. He then heaved it across the court toward fans.
Rose finished the game with 23 points, eight assists, and four rebounds off the bench. He's averaging 18 points, 5.8 assists, and 2.4 rebounds in 35 games this season.