Back on the original topic of the thread-
If I had to guess the nut is probably sitting in the oil pan if you didn't see it in the head. It's probably ok down there, but I'd run something down the oil drain passages to make sure it's not lodged and disrupting oil drainage. A friend actually had a head come back from Clearwater Cylinder Head with improper torque on the cam caps that was partially responsible for the head seizing up. When the head was taken back to them they noticed that another factor had played a part in the failure, but owned up to overtorquing the bolts and rebuilt the head again. No shop is infallible, even a good shop like CCH. I would check the torque on everything accessible just to make sure.