Where are my photos disappearing to???? Lumia 540

[WPCentral Question]

All photos, whether taken using the camera, or downloaded from whatsapp, or copied from pc to phone, they all keep disappearing after a short while regardless of where they are saved (SD or phone). Sometimes all that I can see on Camera Roll is a grey square and when i tap on it i get "can't open because the file appears to be damaged, corrupted or it is too large". Anyone know what is happening.