Dark cigar-shaped UFO near a plane over San Rafael

On May 2, 2015, a man, living in San Rafael (California, USA), was photographing an airplane contrail during a beautiful day. Later, he has noticed on just one picture a dark cigar-shaped object!

Witness statement:

I have been photo documenting Airplane contrails and have taken many pictures. Only in one photo so far have I discovered a strange object.

What is it?