Unsure if you have found it after all.
A prompt appeared for me on the bottom Spyglass (E3) "Look for clues regarding the 'Black Wolf'"
I'm unsure if you have to visit Paul's place first, but there is dialogue over there too.
The FANMADE_GUIDE says the following: "...you’ll be forced to on the second time (easter egg: if you keep clicking “don’t stop”, the options will eventually invert, just to mess with you ;p)." but with a bit of experimenting, I found out that it is possible to let the painting be completed by not disturbing Thane. If you keep on pressing the "let Thane go" option a few times after it inverts with the "stop Thane" option, you will eventually allow Thane to enter the cave and do his thing ... and when you come out of the painting, Thane's painting by the Dragon will be finished and not burned. :)
No idea if it impacts anything other than dialogue tho.
The game is looking great! I absolutely love the concept, and look forward to where it will take us in the future. The story so far is interesting and I look forward to see more of it.
I've played through twice now, once as a pure "virgin" and another where every single enemy wrecked my character ... The difference in progression was pretty fun, and the first playthrough was quite challenging without the skills and passives from the Soul Gems! There are a few scenes that don't fit in well tho, if you avoid surrender at all times. Maybe I'll try taking note of these at some point.
TL;DR, thanks for the great experience! I look forward to the future of this project.
PS: I wonder if we'll get "The Shape of Water" experience by bothering the fishes in the fairy cave, in the future ... ;)