Thanks for the input.
To be more specific about what happened, I missed an upshift and gunned it in "false neutral". I could feel and hear rattling in the transmission, but I was already committed to passing a car. I mashed it into gear and got back into my own lane, but the rattle kept getting worse. As I stated at th beginning of the thread, I managed to get to the shoulder before the rear wheel seized.
I am fortunate it did not lock up sooner. I had my wife on the back. It could have been tragic.
I bought a demo and it has been nothing but trouble. I took it in in earlier because of a noise, and they found it was due to a bearing that had been installed backward at the factory. Triumph only partially paid for the repair since it was out of warranty.