Hello gab. Are you saying, that you simply removed a smartphone from your Norton account by mistake? Reading further did you reset the phone to factory? For the former, you can simply reinstall Norton and activate it as with any other Norton product if you have a Norton license for multiple devices on your account. For the latter. If you factory reset your phone Norton cannot recover that data unfortunately.
Did you use the Wipe phone option from the Norton Account web site? If so, as SoulAsylum noted all data is lost.
If this is the case, your best hope of recovery is with the Restore function in the Settings of your device. Your Google Account might have your data backed up on an Android device, or iCloud may have your data for IOS devices. Of course this depends on whether you set up those backup features.