Where is it mentioned that Gon didn't get his Nen back after being healed by Something/Nanika? I watched the entire Hunter x Hunter series and I've just noticed that it is not stated whether Gon got his Nen back after being healed by Nanika or not. And I'm curios... once he jumped so high on the Wolrd Tree (we also have to notice the speed) is it possible that his Nen was restored? It would be impossible for a person with the qualities of an avarage human to jump so high/be so fast after all...
I believe that Gon's aura is still there just not nearly as much as before. i think he gets it back or something because after Gon meets his dad and he and Killua split ways, Gon and his father fight together in the Dark Continent Arch. I'm not sure what happens in that arch yet because I haven't read the manga just yet.