Grey Meadow, the Industrial Hub

Well they do in SSV because they are programmed to - I am talking about when you add a lot to the bin with ghosts on it and then use that lot in the world - that sometimes it is like the ghosts get stuck in the transition and they won't come out - but mourning them will or at least did seem to jump start this issue. Where you didn't see them in that lot, you may have been playing the added house, but they were possibly stuck and why you probably did not see there were ghosts there. I generally don't wait to see if they will appear with a binned lot, and just make the family mourn them the minute I move a family in - just in case.