How can you not know your ID; you just have to click on your profile and check top right to copy it.
Yes, that’s how you can get your account ID in normal circumstances. But unfortunately for him, he can’t do that since his account was blocked and he obviously can’t access it anymore.
But I believe the email address he used to register at the casino will be more than enough to identify his account. Now that robelneo has forwarded it to them, all we can do is wait for their reply.
Good luck with your bets, by the way!