Missing Apple Software Updater after using a driver updater

If you mean you downloaded some sort of Apple software updater, then ran that software and now the original updater package you had downloaded is gone......that is probably because after the software was installed, it presented an option to "Move to Trash" or "Delete" as the default highlighted option for the right most button to click where an "Ok" button is usually located. There is also another button to keep the installer.

You can either download it again, or recover it from your backup.