Leaving Derth before killing the elementals breaks things

[Zonk]

After entering Derth for the quest, I decided, for some reason, to leave and return later(wanted to check something). When I returned...the elementals were no longer there, but the quest had neither failed nor advanced. I was however stuck(at least I think - I didn't try visiting Angolwen..)


So...what's up?
Was that supposed to fail the quest, in which case I'd want a warning before taking the stairs?
Was it a bug with the elementals not spawning again..?

[Zonk]

Bumping this because I just had it happen again - as coming back from the Eidolon realm didn't break the quest, I thought going back to the wild and then returning wouldn't either...