Your authorization serial number is emailed to you when you purchase, so it will always be available to you in your email account.
This serial number is also always available to you from your Surreal Machines online user account. If you purchased from Plugin Boutique your serials and downloads are similarly available at your account with them.
If you ever have any authorization problems that cannot be solved via your account, contact support@surrealmachines.com and we will help you as quickly as possible.