How big was the threaded screw thing? Did it look anything like an oil journal plug? (since one was missing before it seems reasonable to ask) How did the combustion chambers and valves look? Have you figured out where the coolant came from?

Definitely check the rods for straightness and length, I would replace the ones from the damaged holes for sure. Check the valves in 3 and 5 also in case they got slapped by a piston. Have the block checked for cracks and the crank checked for straighness and cracks.

And go back to the engine builder to get some money back.

Pat