Simply disengaging the Wyrmslayer and escaping is always an option, of course, and an easily credible one at that; the only real issue with that solution would be that Salas would end up leaving the Anaxim Forest on foot, whereas Jillian and Gerald left on dragon wings... in other words, the characters closest to Salas would end up a day's worth of travel away at best. It could be done (presuming, of course, that it would not be out of character for Salas to do so; forcing a character to do something it would actually never do is never a good solution), but it may not exactly optimize the roleplaying experience for you.
The main requisites of my idea is that Salas survives the battle, either by fleeing Gariel Downs or by being injured to the point where the crusaders would ignore him for the most part, but stays within the forest itself. Escaping the fire would technically be possible, especially if he stayed in Gariel Downs where there are no trees nearby, and the towering Gariel Rock sheltering the area from the wind. The crusaders would move on soon after Jillian and Gerald's escape, by the time of which the battle irrefutably ended, and Gariel Downs would be safe; littered with corpses of crusaders, defenders and beasts, certainly, but relatively safe. Regardless the point would be for Salas to have remained in the forest, since Renold (the green dragon with Jillian and Gerald) mentioned to Gerald in an earlier post that the highest of the Guardians of Anaxim, Crone, stayed in the forest to finish some business before fleeing herself. It would be quite likely for Crone to go to search the forest for survivors and consequently discover Salas. Crone is also coincidentally an extremely powerful sorceress [I]and[/I] healer, so she would be fully capable of mending Salas' wounds, after which she would be liable to teleport both of them to where her second in command - Renold - had gone, which just so happens to be where Jillian and Gerald are. That way he could rejoin those two immediately, rather than having to chase after them for who-knows-how-long until he caught up.