Two weeks ago, my coolant light was on, and my mechanic replaced the coolant res

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5 days ago, white smoke was pouring our from the tailpipe. The mechanic said I had an overdue oil change. The smoke continued., and I brought the car back in. Today, he says one of the pistons became loose, and pushed through the exhaust, causing an oil leak. Did this problem occur because of an incorrect repair of the coolant reservior?