2003 Hyundai Santa Fe Harmonic Balancer

Drive Train Axles Bearings problem
2003 Hyundai Santa Fe 4 cyl All Wheel Drive Automatic

I took my wife’s 2003 Hyundai Santa Fe over 100K miles, in for what appeared to be a blown power steering pump. The mechanics diagnosed it as a problem with the harmonic balancer between the crankshaft and motor. As it was explained to me the harmonic balancer maintains the balance between the tires, crank, motor and transmission. The mechanic also explained they that needed to remove the balancer to check the key and crank shaft to ensure that they were not damaged. I left the vehicle to be inspected, an hr later I get a call stating that the crank shaft had fallen off the car and needed to be replaced. Along with the timing belt, water pump and various other things?

I’ve never heard of a crank shaft just falling off a car, my questions are?

What could have caused the crank shaft to fall off the car?

Could the mechanics had failed in following the proper techniques to inspect the crank shaft and ensuring that no further damage was down to the car?

Are there any other common problems I could have with this car in the future?