I think he has lost his account username, not his password. If you've lost your account's username, you can send one of the admins a private message with the following information: 1) Your character names 2) The date of birth associated with your account 3) The email address associated with your account Also add that you are missing the account's login ID.
Oh but when you click on that link, you'll see that when you lose your account information you have to send a msg to one of the admins. That's why i send that link.
I think it's better to refer to this page instead: https://royals.ms/forum/threads/troubleshooting-contacting-a-gm-guide.74521/ Spoiler: Taken from that page I've sent a reply to your message.
To clear up confusion, I edited the 'password/account recovery' sticky with the same information as the Troubleshooting/Contacting a GM guide.