I will say that over the many 50 plus years of motorcycling, snowmobiles, go karts, etc, I've never seen a cable break within a housing.
I can see how it could though of there were a very bad kink in the cable housing, like through a grommet or a piece of metal has caused a 90 degree turn. But I would think that the cable in those cases would not operate freely enough to function without a tremendous amount of return spring applied.
Either way a new cable will be needed and while re-routing the new cable, check for free flowing bends and no sharp bends.
Good luck with your fix.
