It's actually user name, like "lddavis" or "Whitefocus13". (Link to member profile: http://www.focusfanatics.com/forum/member.php?u=79824
Look at the top right of the page. You should see a line that says "Welcome, Whitefocus13". Two lines down, you'll see "Private Messages". Click on that, and you'll get to the PM feature. PMs are like email, but limited to just the forum members. On the left hand side, you should see a menu with a bunch of options. "Send New Message" is about halfway down. Put "FordCustomerService" in the "recipient username". In the message box below, include your VIN number, or dealer number and order number if that's all you have, and they should be able to look up the status of the car.
Link to PM section: http://www.focusfanatics.com/forum/private.php