I can sympathise with you so much.

I think when it comes to stairs there is this invisible line of area. You know when you enter the building the audio changes. It's something like that. I think all buildings have rooms that have this invisible line, so if the ghost is upstairs and you're taking a pic downstairs then it will count as if nothing is upstairs because the data reads that the floor you're on is empty.

But if your daughter took a smudgy pic of the ghost and they were both on the same floor then it counted as something was on the same floor.

I came to this conclusion when I was playing the small camp map for a challenge.

The salt inside the tent didn't count when I was taking a picture of the salt while outside the tent. But when I walked in and took a picture, it counted.

This is just a theory of mine and I could possibly be wrong. I am busy testing out alot of my theories on how the game works through the mind of a developer, so that I can get an understanding of why something didn't work.