Ghost of a Child in my Photo?

I was sorting through my photos of Scotney Castle and in Photoscape I saw a shadow in the bottom left window pane. I zoomed in and saw what is clearly the face of a young girl. It is a bit blurred and indistinct but it's definitely there. I do not remember anybody being in the room and I simply cannot imagine that I would have taken a photo if there was somebody, especially a child alone, in the room. It was near the end of the day and my sister confirms that she does not remember there being any children there at that point-just a handful of adults.

For me the strangest thing is how sad the girl looks.

I might contact the castle and ask if there have been any sightings of ghosts in that room.

You may have to save the photo and zoom in.

I'm sceptical of many ghost photos but can't think of any other explanation...