Up date.
Thanks for all the input. I've always used safety chains but unfortunately in this Blue Ox design they hook to the same base plate and did not have a separate connection to the chassis. I believe base plates after mine came with a cable set to attach the plate to the chassis.
After closely examining the threaded end of the separated tow leg, its more apparent that the rod did not break but became un-threaded or whatever it is threaded into broke. The rod was heavily abraded by dragging it on the concrete road surface. The real clue is the pealing of the metal over the edge. Whatever happened, its a lousy design.
I had my beefed up baseplate thoroughly inspected today and found in good condition. Also I now own a new Road Master towbar.