Having mulled this over, I have decided this is like one of those TV episodes of CSI (or whatever) where they get instant results by spurious methods.
My answer, based on no factual evidence whatsoever, is that Thomas certainly is in the photo. Based on TV crime-solving theory, Thomas is taking the photo. A nearby glasshouse has reflected his image and this can be seen reflected in the left eye of the donkey in the photo.
Do you think CSI or even Hetty Wainthropp will be calling me soon to offer me a job? Hetty Wainthropp…there’s a force to be reckoned with.