A friend of me tried to reset his password but it says account does not exist and neither is his email known.

He wasn't an active resident during the transition to the new website where all OsGrid residents were asked to activate their accounts for the new site; so I'm afraid there is no way for him to recover his password?

What is the procedure exactly to recover?

Hi Lotek,
You will need to contact the Admins to get the account reset - I don't know if they have a procedure for email addresses that you no longer own though.

If you email them, or use the IRC channel that would be quickest, or contact them in-world on your friend's behalf.
https://www.osgrid.org/?q=node/8

Ta,
Scoobs X

Hello

Password lost for a user not migrated in the new website:

Need contact the administration directly in the form contact of the website.
on this link https://www.osgrid.org/?q=contact
and :
Category: password Issue

Please enter all informations needed and the mail used for the registration.
If he have lost the mail concidering this account dead.

Without this informations, this account can not be solved.

We don't make any support in IRC or IN-World for this issue.

Thanks, I'll pass on the info and hope he can get it resolved.