Have you found anything else about the scam activity? I am not familiar with the gambling site but I do not want to conclude the gambling site as a scam. The email might be sent for the account you have created or mistaken even many people who may create an account by taking the email of others to spam or waste the time of others.
This is correct. I have also had a similar experience, and like the casino representative has explained on the second page, it's possible that the op might have had an account with them because it has happened to me once where I wanted to register an account on a particular platform only to notice that my email is already registered with them. All I did was reset the password and regain access.