After watching the last episode I thought about this, when the little doggy entered the swamp and became a spirit again. I'm not sure if the swamp we saw is THE Foggy Swamp, but I guess there's no reason it couldn't be.
"Huu explained that the swamp was a sacred, mystical place and that he had reached enlightenment right under the banyan-grove tree"
That'd also explain why Toph is seeking enlightment there (remember Aang's vision in the swamp).