Fast user authentification

[squishi]

For a vb 3.8.x programming project, I need a page to load very quickly.
Loading the whole forum with

PHP Code:

require("./global.php"); 


takes way too long, especially if there is a high load on the server.

So instead, I wanted to load the user's data (I only need the username!) using the cookie information.
The query would look like this:

SELECT u.username FROM vb_user as u,
vb_session as s
WHERE u.userid = '".mysql_real_escape_string($_COOKIE['vbuserid'])."'
AND u.password = '".mysql_real_escape_string($_COOKIE['vbpassword'])."'
AND s.sessionhash = '".mysql_real_escape_string($_COOKIE['vbsessionhash'])."'
LIMIT 1

The problem:
The hashed password in the cookie does not match the password that is stored in the database. I specifically checked it for my own account. The password in the cookie does not match the password in the vb_user table.

Why don't they match?

How else can I quickly authenticate a user without loading the whole forum?