I load my project today, and the first thing I was greeted with was the fact that my Prefab folder had just disappeared, along with it, the functionality of my Player, Camera, and MusicManager. This has happened for no apparent reason, and now I might have to start updating an older working version of the game.
If your prefabs were moved or renamed outside of unity they may be lost by the project but still on your file system. I would search the project folder in FileExplorer (or whatever you are using depending on your OS.) Also, check your recycle bin. You should have to recreate just the prefabs, not entire project.
Finally, if you have an old version of the project but have updated the scripts, try exporting the prefab but not the scripts or other files from the old project. When you import the prefab it should latch onto the scripts of the same name in the up-to-date project.