Beside of the following two old-way options and browsing, you now can go to the users page and directly search for the users in the filter-elements of the corresponding columns.
 
If you know the ID of the user, you can open the following link user ID link template and replace the '1' in 'uid=1' with the ID you know.
 
If you know the userid (nickname) of the user, you can open the following link userid link template and replace the 'guest' in 'user=guest' with the userid you know.
 
Or you may ask in one of the forums. Maybe someone other knows the player you are looking for.