Gitolite's reflog has been able to help with that kind of problem for a long time, provided you try to recover before the server's next GC (I wouldn't be surprised if GitHub has the right software on the backend to allow this too, but don't expose it on the frontend) – and if you have proper backups, then the GC isn't really an issue either. Careful what you read from Collabnet, as they are really keen to point out the problems you can possibly run into with Git to promote their SVN solution. Part of this problem was their reliance on GitHub.
That all said, because Stash isn't GitHub, it doesn't negate the need for something like this for Stash. Force pushes need to be recoverable, at least for some period of time. Even in the face of proper backups, which could require some fairly substantial time to fetch off tape and could still cost a day of work.