Unity Backdating itself

Hey, I have a frustrating problem. When I started unity today, it seems to have changed almost everything to what it was about two months ago! My animations, components, and most of my scripts that had been worked on from two months ago were all reset. Whats weired is that the scripts/animations/components that I changed yesterday were all still the same though. Does anyone possibly know why unity did this? Also, I do have a previous build of the game that has assets that could be used for the project, but I'm not sure you can decompile a build and use it for assets in a project.