If you are not getting any faults blinking the check engine light, then the ECM is being completely swamped by the fault condition, to the point of cutting off the fuel or ignition, or flooding the fuel so bad the engine wont fire.
That's exactly what got my attention, that there were no CEL lights, blinking lights, or anything.
Troubleshooting is always fuel, air, spark.
My first thought was fuel starvation (filter or pump), but after 40mi of 80+mph, a problem should have presented itself on the highway rather than at cruising at 50mph.
Second thought was air, but for the same issues, it didn't seem likely (and there's a 30 day old air filter in there).
Spark didn't seem likely, as the bike was running perfectly smooth, just felt like I rolled off the throttle. It was smooth all the way to shutdown.
I looked in the tailpipe with a light, and didn't see any blockage. One very bad thing with airplanes is getting a loose baffle that blocks the exhaust and chokes the engine.
That would seem to make sense in that after the engine quit, the loose baffle had pressure removed and fell away from where it was blocking. That would also explain no CEL, in that the engine management is doing everything right, there just is too much backpressure.
But I don't know how MC mufflers are made and whether than can actually happen. The exhaust is factory, and not drilled.