Well this is getting me closer. Thanks Stormy.
Always a pleasure
I didn't have any mods at the time, stormbird, save for some graphic enhancers. In addition, UESP mentions he does occasionally get stuck.
Well no, that was just an example of a how random events kill NPCs. The dragon that killed the smith in Riften was seen and slayed, but the fact that it had murdered the smith wasn't discovered for days afterwards, after I did a casualty check of the battle. .
Bugs- Some players have noted a glitch where Ulfberth becomes stuck on a hill outside the players home in Whiterun and will not open his shop for business.
- http://www.uesp.net/wiki/File:Pc22.png Use the "tc" http://www.uesp.net/wiki/Skyrim:Console command to move the NPC away from this spot.
- Attack him, causing him to become hostile momentarily and move from this location, though this is considered a crime. He will then eventually open his shop. It may take several "respawn cycles" for his vendor gold to respawn.
- You may also sprint into him to push him from the spot on the hill. This works as a better alternative to attacking him, as you don't receive a bounty. Once you've nudged him a bit, he'll continue into his shop.
- Use http://www.uesp.net/wiki/Skyrim:Unrelenting_Force to knock him off his perch.
The fact that he gets stuck on the hill should not cause him to be recognised by the game as killed. He probably died in some kind of fight which you triggered but then did not witness.
That fight could have occurred for any reason - he could have defended you from guards, he could have attacked a dragon, he could have been attacking something and hit a friendly to get an assault bounty.
This is pretty much exactly why this happens.
There are a lot of "events" that occur as a result of an NPC being killed, and in order for them to occur the game needs to check to see if they are dead.
Thanks very much for confirming my understanding.