It happened at 10:30 Friday night on Route 150, near Leroy.
Police say witnesses saw the driver, 46 year old James Odom of Foosland, fleeing the scene on foot before they arrived.
He's a white male, about 5'6, 130 pounds, with brown hair and green eyes.
It's not known why Odom left the scene.
Multiple departments including canine units are assisting with the search.
Meantime, the status of the other driver remains unknown.
Anyone with information on Odom's whereabouts should contact Illinois State Police at 815-844-1500.