You are obviously using vBPortal there.
Well, the $post variables only work in the showthread section since it pulls information from the functions.php - you would need to do a db query to pull the custom user profile fields in contact.php first for this to work.
Like I said before, this has nothing to do with my contact form hack. Please ask this in the PHP forum, or in the vBPortal forums.

I cannot support my hack to make it work with VBPortal - only with vB.