Did the dipstick mechanic actually flush the radiator? If he did not look at the radiator you as the customer should have said something but it's a little late now...and not all mechanics are dipsticks just putting it out there... The answer is depends on what you took the car in for in the first place whether or not that would have had any effect on the damage already done by driving the car without having it checked over ...what I am saying is usually the vehicle will have symptoms a long time before it gives up the ghost..blows a gasket and cracks the block by losing all it's water or boiling over from no oil/water circulating in the engine...I can't say who's at fault for this since I don't know your maintenance habits for your car...only you and the mechanic truly know and the Lord...hope this helped