For civilians, it seems that what is being seen with the eye is not visible to a camera (i.e., it is either imagined, hallucinated, or just not material/solid, etc.). It is possible that what is being seen with the eye doesn't want to be photographed and has the capacity/ability to prevent it.
UFOs are supernatural and can even be summoned (search Dr. Steven Greer), though they can apparently seem very physical. An auntie of mine reports she saw, a number of years ago, a full on 1950s style flying saucer close up and personal. Uncle saw it too, but refused to speak of it when asked (he had sworn auntie to secrecy and had apparently been scared witless by the event).
But I’m not convinced cell cameras are all that great. I can’t take a picture of even the moon. Just looks like a blur.