itch.io

I went back to check and you're right. Normally it should unlock just by seeing it, but here the check doesn't happen. I've added that to the list of bugfixes for future versions. Here I think it was caused because you opened up an old save while you still had not finished the quest "Some relief..."

You can still unlock it, but you'll have to reach the point in the quest where you had to do it for the first time. So that means having to redo a new game or if you have a save that happened before the quest "Some relief..." appeared.