This isn’t the official answer, but to the best of my knowledge this is how it works:
Removing the license removes the file that tells Sublime you registered your copy. “Unlocking” Sublime happens locally, there is no server that tracks licenses or guards against abuse, and you can use your license on any amount of machines. If your work PC is restored to an old backup, they could use Sublime with your license. If they do so this has no consequences for you or the validity of your license. There is no way to revoke a license without releasing a new build of Sublime Text, so this only happens if there is a new build anyway (e.g. for bug fixes) and a license key was found to be shared on a public forum or something like that.
So in practical reality there should be no need for you to have your license changed, unless you expect your previous employee to severely abuse your Sublime install that’s still somewhere in an old backup.