Show Message For Guest On Order Landing Page

Hi, as you all know, a guest user is prompted to register an account on the order landing page. I was just wondering what {if} statement triggers that?

I wish to put in a Smarty/HTML block that says;

If the customer just used Guest Checkout

Show them a message with a small banner image on the order landing page.



Please use

{if !$auth.user_id}

Thank you very much! :-)