Ok, but did you went to visit the merchant before Doyle mentioning her?
Cause you need to visit her, get out of the store since you don't have anything to sell, go to Doyle and when he tags along he'll mention it. I believe it happens theday after the first encounter with the merchant. Then you can get to the attic and retrieve the dagger and ring, then you go to sell it.
And btw, having max stats doesn't automatically unlock everything, it just makes it a little bit faster to do so but you still need to progress and repeat some scenes to advance.