I am working in Lightroom 6. I have PC and have an external hard drive attached. When I open my hard drive in Lightroom is shows a folder titled 2016 with images I have taken in the last several months. However, there is another folder labeled 2015 that does not even display in lightroom. When I open up the drive files on my computer I can see photos in the 2015 folder and they say älready imported. How do I get my files to show back up in Lightroom that have already been imported?