I went on a hike today with friends and took several videos and a few photos. When we went to the pub the first 3 photos had disappeared, so I turned my NEXUS 5 off and on, then all photos and videos were showing, which we all looked at. When I got home and looked again only the first 3 photos were showing and none of the other photos and no videos at all, they had all vanished? Where are they and how do I get them back please??