Honestly I'm just really wondering what the odds are. In particular for code that made it onto git.

Over the long term, the odds reach 100% that it won't be checked out. That's because people mostly only work on newer projects. As for mature older projects, even if they're running in production, cease to see many/any updates, and so they don't get cloned on to newer laptops. This doesn't mean that the older projects are now less important, because if they ever need to be re-deployed to production, only the source code will allow it.