It's hard to find additional details. Apparently it's not newsworthy unless someone (almost) dies. Oh well.

It seems they were backpacking on the south island, so I assume they had a gas stove.

Also, they apparently missed the worst of the snowstorm. Still, temperatures dipped down to 17F. The SAR spokesman suggests there could have been a different outcome without the hot pools, which they used to fullest advantage. I'm not sure that a Wisconsin boy would fold up all that quickly in the face of a little brisk weather; but NZ has a lot of very young mountains, and I'm not sure there's much suitable vegetation for shelter and fire.