My materials all vanished in my project

I am very new to Unity and game programming. I still don't understand or know much about it so sorry if I can't explain this very well. I am watching a series of youtube videos and creating and learning from what they do. Basically I am copying the making of their game to get Unity down. I imported a project file for a different version of the game to experiment. It was a zip. In a series of screw ups Unity wouldn't load since it starts by loading the messed up default project. It reported a bug (from the imported file I suppose). I threw various things in the recycle bin and had to end up restoring some of those when I realized what was interfering and what wasn't. Now all my Scripts disappeared for what I set them to (ex. sphere says Mono Behavior and for its script says Missing (MonoScript)) and all my materials are gone. When I went to mesh renderer and element 0 to add the element material they were all blank. The particle textures for those element materials vanished. How can I restore that without starting a new project (new projects and different projects those particle textures haven't vanished only the messed up project did that)?