I am lost here as relative Aperture novice. I have a lot of projects where there is a preview images  where I can scroll over the project folder image and see all the photos that look they should be inside, but it shows 0 images on the bottom right and sure enough there are no images when I open up the folder. What’s going on here? Are these images somewhere else I hope? Is this some type of an image ghost? Any help would be greatly appreciated. Thank you.