Hello,
When you Netfile with TurboTax you will not only be shown a page giving you a confirmation number but will receive an email with a copy of that confirmation. Further, in TurboTax you will note in EasySteps left menu in the 'File' section you will see that the return has been filed and the confirmation number noted. When you go reopen the file from the saved file for TurboTax Desktop or from the Return Manager in TurboTax Online, the files will be annotated with the confirmation number noting that it was filed.