I've had this experience more times than i can count. Not with flying saucers, but with all manner of terrestrial things - animals, vehicles passing by, people

I've had this experience more times than i can count. Not with flying saucers, but with all manner of terrestrial things - animals, vehicles passing by, people doing things. You see it, you look at it for a bit, you think you should take a photo, and by the time you have your camera in hand and switched on, it's gone.