@worldhistory@histodons whilst I have not personally witnessed ghostly additions in photos, I have had direct personal experience of somebody who was present not appearing in the developed photo.
Several of us were reading the words of a song pinned to the back of the girl in front, but in the final photo she is missing from the chorus line. We are all looking at an empty space.
A long time before photoshop; the photographer was unaware until it was pointed out
There was never an explanation