Mortimer Goth died pre-patch. I wasn't controlling his household at the time. I've gone there now but I can't find his urn/tombstone. He's in Bella's relationship panel and his picture is a ghost, but...
You need the urn/tombstone. In the daily chat one of the SimGurus said that Sims who die when you're not there don't leave an urn/tombstone because it would clutter up the world. I had an elder Sim die when I was playing another family and she didn't leave one, either. Anyway, apparently no way to get them back.