Update:
16 months after first contacting Enterprise to resolve this, after emailing two of the contacts listed above (I'll let you guess which two) and two more executive contacts I found elsewhere online, I received a response from the 4th executive. There was absolutely no response from the first three I emailed. The gentleman who called me lightly apologized and committed to issuing a refund check. He had no response to why Enterprise local office, Enterprise Corporate Resolutions Team, and three other Enterprise executives completely ignored me.
Check arrived via Fed Ex the next day, and cleared, so I consider my issue closed.
I will also never willingly rent from Enterprise again. If I am forced to do so by insurance or auto repair, I'll use Segments advice above...