Black flying saucer over Highland, California

On October 11, 2014, two friends take scenic photos near the city of Highland (in California). Later, one of them noticed a black flying saucer on his image. This UFO was no visible at naked eyes. What is it?

Witness Statement:

I was off-roading with a friend and coming down some of the dirt roads from Big Bear to the 330. We stopped in a few locations to take scenic photos. A few weeks later as I went to edit some of the photos I noticed an object in the sky that neither of us had known was there. When I magnified the digital image I could not identify the object.

For most of my life I've been interested in, and am knowledgeable in civilian and military aviation. I feel that if we had a conventional aircraft flying this close to us we would have not only heard it but noticed it visually. Neither of us saw anything even close to this for the entire day.

Under magnification the object does not look to be organic, and doesn't fit the profile of any type of civilian or military aircraft.

The photo was taken with a Canon Rebel SL1, at 18mm / 1/160th / f11 / iso 100

Because the shutter speed was 1/160th and there is not much motion blur this leads me to believe the object was not moving very fast when photographed.