Bug: Game unwinnable, no Bell of Opening

[mobi-leuser]

mobileuser on hdf-eu Playing Cavewoman, briefly became Valkyrie, switched back to cavewoman later. It's possible I briefly visited the quest nemesis level as valkyrie, not sure. Came back much later. The nemesis (chromatic dragon) started peaceful. which is already strange. Killed her. The quest artifact was there, but there was no bell of opening, making the game unwinnable.

I suppose there is a bug with changing roles. Is there anything that could be done about my save to make it still winnable?

[mobi-leuser]

to reproduce it might be necessary to save and load, so start cav, become valk, save+load, enter chromatic dragon lair.