This article or section includes speculation, observations or opinions possibly supported by lore or by Blizzard officials. It should not be taken as representing official lore.
Following the battle on Hyjal, a furbolg took the corrupted Idol of Remulos to Thistlefur Hold in Ashenvale. As there are no furbolgs on Hyjal, it could be speculated that it was Barkskin furbolg. As such, the Barkskins could have become the Thistlefur furbolgs.
The furbolgs that lived in the Barrow Deeps beneath Hyjal and were saved by Tyrande Whisperwind could be members of the Barskin furbolgs as well. Alternatively, they could have been the Felwood Furbolgs that Tyrande helped earlier (given both furbolgs Tyrande interacted with were shaman and the second one had to thank her again), or the Timbermaw furbolgs.
They are often the basis of furbolg Alliance playable race rumors, speculating that they survived and remain uncorrupted.