I ran into a bug on a side quest, "A study in blood."
I went through the window in the artist's house and waited for an unusually long time for him to go upstairs (I think that was just because I had to hide in the room rather than stay waiting in the adjoining room), and then successfully stole the portrait. There were no yellow pop up words telling me of my success and to go back to Sabina, but the purple marker on the map changed to her location which made me think I could finish the quest. However, when I went back to Sabina's house and double clicked to talk, no dialogue box popped up: it was just generic 'good luck' and 'don't stay long, it will seem suspicious' as if I hadn't just successfully completed her task. I can't give the portrait back to her because of this, it's taking up space in my backpack and I can't get my quest reward and experience from her...
Please help, thank you.