Has anyone else had this happen?

I came to the Lilith Quest, where you have to go to the cave in Tangle Tree Forest. There you have to kill the Hive Queen. Once she's dead, you have to take her stinger, and present it as proof you killed her. The problem is, without knowing this cave's importance, I went there before receiving this quest. The result is the Hive Queen did not appear, there is not stinger to present, and no way to complete this quest.

Shall we pause for a moment to utter an expletive?

Done.

What I'm rambling on about is there are apparently breakable quests. The side quests don't seem to be breakable ( I came to the slider chest in the abandoned house and tried it open it before getting the quest. After getting the quest, I could open the slider chest without any problems.)

The Main Quest seems to have breakable components. Which is a pain, as my character is Level 9, and I'm enjoying playing him.

Did you try going back into the cave after getting the quest to kill it? I suspect entering the cave with the quest active might make it spawn.

Check this page to make sure you're looking in the right location for it http://www.gamebanshee.com/eschalonbooki/locations/whistlingcave.php

If it still won't spawn though you have the quest, I think there's 2 things you could try.

You could reset the zone/region by deleting a file, resetting the region means it will be as if you've never entered it so that should work. Though I don't remember enough to tell you which file to delete but posting on the games forum or even searching should help there.

Or you could try a save game editor and try adding the quest item from killing the Hive Queen to you inventory.