Premiere Pro CC render issue

Has anyone else had this issue or know of a way to fix it?

I've been rendering 4k footage and I make sure that I save after each render is complete. I shut down Premiere. Later, when I go to open the project, some video files are registering as unrendered footage, even though I spent over an hour rendering them previously. I've definitely saved before shutting down the program. Why won't the render stick?