Nothing has given me reason to decide whether ghosts are real or not, and if they are real whether they can be captured in a photo but I think that your "ghost" may just be a drape or something of the sort. Probably something you didn't notice while you were walking through the house.
Please understand the art of spirit photography is difficult and some even believe that it cannot be done with a digital camera. I know for certain that you cannot capture an invisible ghost in a photo.
I would suggest reading up a little bit on spirit photography and learn the mistakes that a lot of people make when believing they captured a "spirit" in their photo.
It's pretty hard to take photograph of invisible stuff, yes.