Images folder in Robohelp 7 project only lists a small fraction of the images actually there

I added an image to a topic. The image had an identical name to an existing image in the project. The image appeared in my main project folder, which is where all images initially show up in my project. I then move them to an images folder. I moved this image, expecting to get a message asking if I wanted to replace the exsting image with the same name. i wanted to update all instances where this image appears. Instead I got a message that this file was in use and could not be replaced. I clicked on my images folder to see if the original image was in a topic that was open and maybe that was why it would not overwrite. At this point i noticed most of the images in the folder were not listed.

I can use Reports Used and I see all the files that are supposed to be in my images folder, but when I go to the Images Reports tab, only the files that are listed in my images folder in the Project Manager are shown. So Robohelp knows the files are in the images folder and that they are in use, but it does not recognize them as images and will not list them as such.

i have no idea how this happened or how to fix it.