I have now gone though more then 10 loops and whited out every option in the tea scene.
Ah, I see the problem, Carla needs to be Corruption level 2 for you to have the option to find it. So turn that down for a run.
Found it maybe if this was my first version I would have gotten it during normal gameplay, but I think that the moonstone was added after I had fully explored all lower level corruptions.
