It happened to me on the lvl 9 quest with the cheese. I finished the quest way back when but somehow today at lvl 27 I ended up picking up the quest in the dead cheeseomancer's store. Yet I don't think I ever had the quest in the first place till today. I think what happened was that I had ventured around on the map saw the place and went exploring.

So how do I finish the quest if its already been finished?

How did you open the portal without first getting the key from the store?

I had all the figurines I don't know man its kinda screwie. Like I said that was lvl 9 - 10 and I'm 27 now.

Sounds like they need to make those Bull & Lizard keys stay as quest items permanently, or make them unique so you can't buy them a second time and retrigger the quest.