Rufftoon's synopsis is a bit off - basically, it took twenty more years for Aang to be found. In that time, Zhao killed the Moon Spirit, waterbending ceased to exist, and the Fire Nation became the Fire Empire. It seems that Katara and Sokka still found Aang, but the dynamic is different - he's a kid being escorted by two adults. Zuko never gave up the search and refuses to do so, though he's mellowed out slightly and became a bit wiser. It's Dead Fic
, or rather Dead Comic, but I liked how despite the bleaker tone it wasn't without hope and humor.