So I think I found a solution to the problem.
My images were disappearing as well if I left the slide show on too long or if I shut off the computer and brought it back up again. The answer, for me, was that the pictures were all “temporary.” In Power Point, pictures added to a presentation are saved to the presentation separately. In Libre, they seem to auto link to wherever they came from.
I’m not a computer geek or anything so if none of that made sense, I apologize. The solution, however, remains unchanged.
I added a file on my desktop “Presentation Pics” and threw all the pictures I wanted in my presentation into the file. Then whenever I wanted to add a picture, I would click “Insert,” “Image” and browse for the picture within that specific folder.
Any pictures you drag from the internet or seem to drag in general don’t seem to stick. Or if you add a picture and then later delete it, or add a picture and later move it, will cause them to eventually disappear. I’m guessing this is because it acts more as a link to the picture and/or a clipboard feature when you move a file and it cannot link to the image anymore? Save yourself the trouble and create a specific file for your presentation images.