it sounds like you are using the Standard Dreamweaver insert record behavior. the tutorial is centered towards using the Data Assist insert record behavior and will not work correctly when using the Dreamweaver insert.
The way the random session works is tat is created each time the page loads, if you store the random session in a form element and use that to save to the database, you will end up with a different value in the database from what is included in the email.
by using theData Assist insert, you will be able to use the session binding in the insert behavior so that the same value will be saved to database as isn sent in the email.
and do follow steps 11 and 12 as written in the tutorial when configuring the insert.