Invisible UFO caught over Sedona, Arizona

On April 20, 2017, three persons were visiting a chapel in Sedona (Arizona, USA). On that trip, they have taken a photo of an unidentified flying object not visible to the naked eye. What is it?

Witness report:

I was visiting the Chapel in Sedona with my Mother & Sister and took several photos of both the chapel and the various views around. It was only after I returned home and viewed the photos on my home computer's 27 inch monitor that I notice in one of the frames that I was taking consecutive photos of my mother & sister that I notice an "object" in the background above the mountains in the sky. This object is only visible in the one frame and is not shown in the frame before and after in the series of photos that I had taken that afternoon. I did not witness anything in the sky with my naked eye nor do I think anyone else noticed anything as well.