Dunkelzhn, Zebulon, and Ghostwalker all basically ended up on extended Metaplanar quests. They could only do so because they had anchors to the meatworld: the Dragonheart, the souls stones, and Ghostwalker's body respectively. That is something dragons can do that metahumans cannot, owing, it would seem, to apocryphally spiritual origins. Lofwyr did the same thing in Ragnarock when he anchored his spirit to Tommy Talon to make Alamais think the golden wyrm was dead.
I'm not privy to all the details about Feuerschwinge (and even if I were, I wouldn't tell you), but as I recall the German government never recovered her remains. It's also been established that radiation and mana have unusual interactions, to say the least. I suppose it is not purely coincidental that when Pegasus translated Street Legends, two of the four entries they added were for Kaltenstein and Nebelherr, the two Great Dragons that were present along with Lofwyr when Feuerschwinge died.