TH,
First, please stand corrected if you thought I was suggesting your problem was related to service provided by Hendrix. My suggestion to call Hendrix was based upon the fact that they are experts in servicing wires and could possibly provide some knowledgeable recommendations.
As I understand, you would like to slide the spoke through the wheel hub and install it into the existing nipple. However, you would first need to extract the stub of the original spoke.
If the original stub broke flush with the nipple or close to flush, I would carefully grind the stub level & flush and then drill a pilot using a Dremel and a very small drill. With the pilot in place, I would then take the chance of expanding the hole with progressively larger drills until I could chase the threads with a new spoke.
The problem with my suggestion is that drilling a pilot and widening is both very difficult and places the drill tip too close to the tube for comfort. Also, the debris resulting from chasing the threads would be pushed into the wheel and might result in tube ware or a puncture.
Sorry, but I would dismount the tire and install a new nipple and spoke.
Good luck,
Ray (64BJ8P1)