When I click on an image to save it and go to look at it in my camera roll, it isn't there but an old pic I deleted is. What's happening?

Sometimes I see photos I like and save them to use as reference for various projects. Lately when I save the image and go to my camera roll for a better look, the image I saved is not there but an old photo I deleted is in it's place. The old photo shows up in the thumbnails but if I click on it to view it, it's a black square. What is happening?