So I downloaded a pic in GMAIL and it went to the downloads folder on my sdcard like it should. It was also the thumbnail in my pictures for downloads. I then deleted the pic and downloaded some more pics from a GMAIL message. However, the first pic I downloaded is still displayed as the thumbnail for my downloads in photos. This is the case even after I deleted the pic and it no longer exists on my phone. What can I do to make the phone not recognize this non-existent pic anymore as the thumbnail?