Stuck on lvl 40 dungeon quest

I'm currently stuck on a quest called Monster of Plant Clan went Berserk. I was suppose to complete a dungeon and collect a high tech weapon and so i finished the dungeon but i failed to collect the high tech weapon and now i can't go back in the dungeon anymore. If i give up the quest, can i pick it up again or will it disappear forever? Any help? I'm seriously stuck and i don't want to loose this quest because that would mean losing the rest of the storyline.

You can give it up, and simply just return to the NPC that gave you the quest in the first place, and start it all over.

You won't lose the quest forever, it will show up again under your quests as if you never started it.

Hope this helps.

When you get to the end of the dungeon it will say you completed the dungeon but you still have to find the item in the last room. it's on a table in a corner and looks like a bottle.