[n4mwd]

The nut has to be in there somewhere. Its not going to get sucked into the oil intake because of the oil pickup screen. You should probably pull that off if you haven't already and check to see if it got washed in there. Once the screen is off, you can stick your finger up in there and feel around for it.

While you have the clutch cover off, check to see if the cam chain guard under the crankshaft is still there. That will tell you if the cam chain was affected.

I still think the overheating is a separate issue. You just did the valves so I don't think they were out.

Oh, and you'll need a new oil screen gasket. They aren't that expensive, but since they are paper, you can make your own out of gasket paper.