Hydrotex

Hi everyone. This is my first post. I'm in a pinch an so is my mechanic. I'm aware that my 92 SC400 is a non-interference engine. I just had the water pump and timing belt replaced. I'm told the mechanic manually turned the engine crank with a wrench and that he turned it two revolutions the night before, and that the next morning he decided to turn it again, but the engine was stuck(locked up). Does anyone know why this may have occurred? Any input would be greatly appreciated. Thanks