Craig Morrell was struck by the bonnet of a green Citroen Berlingo van as it accelerated out of the yard at Swanglen Metals in Bingley, near Bradford.
CCTV footage shows foreman Mr Morrell, 47, being thrown in the air as a result of the hit-and-run and suffered a badly damaged vertebra and a broken finger.
Swanglen’s managing director, Dave Allen, said Mr Morrell had tried to stop robbers making off with a Kawasaki motorbike belonging to his colleague Alan Harris.
Mr Allen said: “It was unbelievable - Craig could have been killed or landed on his neck and been paralysed. It could easily have been so much worse.