Sorry guys. I failed to tell the whole story. I bike a lot. About 70 to 100 miles per day. I have been told by the experts to change the chain every 2,000 miles and the cassette also. Of course I do not do that. But every so often I remember it and tell the LBS to replace that stuff.
Following that accident I told them to do that hoping that clicking sound would disappear.
Well, it did not.
Two experienced mechanics and me the Engineer agonized about that clicking (very faint) sound.
It was a bend crank.
It is only Money.