SPOILERS ahead about a minor sidequest:

In the rail nomads camp, I found the drug dealer. Then I saved. When I talked to him, he told me he wanted some radioactive mushrooms to make drugs. So what did I do? Realoded my save and killed him, and then reported to Kekkabah.
Later, I found the mushrooms, but now they are sitting in my inventory and I have a quest that says there's someone in the camp that may want them. It's obviously talking about the drug dealer, but now he's dead. I tried selling them to a merchant, but I couldn't.

Did I fuck up? Will that sidequest be in my log forever and the shrooms in my inventory? Is there another way to get rid of the shrooms and complete the quest?

Edit: oops, I forgot to mark this topic as a question.

Unfortunately, you'll be left with plenty of useless quest items and unsolvable quests before the game is over.
Remember that you can put the quest items inside the chest at the citadel. At least they won't be weighing you down.

Thanks for the answer. I'm pretty OCD about these things, and that's why I feel overwhelmed about unsolved sidequests in The Witcher and Planescape Torment, for example.

Don't eat the radioactive mushrooms.

Good advice: save often and on different slots. Due to bugs I had to follow one major questline four times before I was able to solve it the way I wanted.

I have a question about this quest. I solved it. Gave the guy the mushrooms, he thanked me, called me a "nice lizard" and that was that. Is there any more to this?

Nope. At least none that I aware off. Its save to rat him out now for even more XP :D

Not trying to be an ass here, but wanting to complete all quests and just killing people without the need to do so doesn't go together. Surprisingly or maybe not that surprisingly after all... :D

Yeah. Did that. Lots of Choppers went to his door. :)

This quest feels like one of those cut content cases. Like the Abishai quest in Smouldering Corpse Bar in PS:T.