I exposed Elrath, but did not grab the potions for the Grey Death. I turned Elrath in, and they went to arrest him. After that I realized I had to go to his house to get the healing potions, but I could not get back in. Lockpick #5 did not work, searched everywhere for a key, etc. etc. No way to get back in. Is this a bug, or do you just "fail to solve quest"?