User blog comment:The Dragon Demands/The History of House Targaryen. Part IV: The Dance of the Dragons/@comment-5014364-20131202200753

I want to make this explicit about the four surviving dragons, which the Westeros.org thread mistook and then just ran with: Silverwing, the Cannibal, and Sheepstealer were mentioned. Ran/Elio then said "four survived, it must have missed one"

...Stormcloud, Aegon the Younger's dragon, was sent to the safety of Essos and rode out the war.