I assume Haynes was paralyzed in competition.
In the past few years the rules have been changed so that riders keep certain numbers from season to season. It used to be that every rider had a new number each season based on the previous years ranking, but that was confusing to casual fans. Now only the #1 plate is up for grabs on a year to year basis.
Haynes broke his back in 1993, and was paralyzed from the waist down. He did it in competition. He is, like James, from Florida, and was an inspiration to James when he was coming up as a mini-cycle racer. Stewart wears #259 in honor of his friend.