First, you're mistaken about the database photo not showing up as a thumbnail. If you write the first post in a new thread and then add the ATP BB Code of a database photo to the post, that photo will be the thumbnail of the thread.
A message does pop up if the image is exactly like the one already in the database, but sometimes subtle enhancements have been made (in sharpness, contrast, brightness, etc.), and those changes keep the system from recognizing the photo.
