The blue box-style delivery van was reported to have collided off-road motorbike in Oldgate Lane, Thrybergh, at around 2pm on Friday.
South Yorkshire Police today released details of the collision as they appealed for witnesses.
A spokesman said: "It is then alleged that the rider of the off-road motorbike, and two unknown men driving another vehicle that pulled up at the scene, threw bricks at the blue van causing damage.
"One of the men is believed to have assaulted the driver of the blue van, punching him in the face, before the off-road motorbike and second vehicle left the scene."
Officers want to speak to anyone who who was in the area at the time as well as witnesses to the collision or assault.
Email [email protected] or phone 101, quoting incident number 603 of May 26, 2017.
Information can also be passed to Crimestoppers anonymously on 0800 555 111.