WOW!! I you have a LOT more self control than I would have. if the Tow truck guy backed into my car.....I would turn into the Hulk!

is it a low pitch knock, or a very fast pitched one? #3 misfire..... I would take the plug and wire completely out. look over the plug for any hair line cracks or damage......

also check the plug wires...be sure that they match with the correct cylinder.