I also think that the speed with which the decision was made probably prohibited any extensive 'Secret Weapon' marketing.
I was told recently that Tussauds actually visited Knotts and Cedar Point and chose Stealth for Thorpe before Rita was even thought of, even though Rita actually opened first. So basically they had Stealth on order and thought, "you know what, we'll have a quick 'below the tree line' version of that for Alton too" and Intamin delivered a short time later so no time for any SW campaign.