No problem, click on the "Recover Account" bar under the "Sign in" bar. You can then enter the last four digits of the credit card and email address you used when purchasing. You will then receive your Order number/ID to go back into the Membership Payment Portal HERE and log in with your Order number/ID and email address.
You may also contact us directly at experience@legoland.com and provide your first and last name and email address and our Team can assist further.