the pulley coming off would have damaged the internals of the motor before it damaged anything outside, unless that bitch flew off like a boomerang. the crank pulley has a dampener and a balancer in it which helps keep the moving bottom end parts moving smoothly and it absorbs vibration. the crank pulley coming off would have just let everything go crazy, but if it wasnt for too long you shouldnt have much to worry about. its most likely a loose belt making the noise, when the crank pulley came off it may have tweaked the tension on the drive belts which should just have to be retightened and more tension put on the belt and hopefully it goes away.