Sigurd can be hard to spot.
I had trouble finding him when I went back to report the kill. He was in a corner out of sight, but a another NPC (just labelled Human) was walking around in the house.
If you do get the quest from Sigurd he tells you that Groblar (?) lives next to him - which he doesn't, he's across town in another street. So you may be checking the wrong spot?? Not essential anyway. I skipped several quests, including the libary ones.
