Usually deals like that are a choice between 1.9% (or similar) OR 'X'-amount cash back. If there was a deal it's possible your sales guy gave you the better of the two options, which would be lower interest.
To be certain, just call your dealer.
I did a quick google search and there are some deals floating around out there.
Example: This dealer has this deal and others right now Click Here
EDIT: Here's a link to the offer I think you are talking about. Again, call your dealer to be sure and find out if you qualified at th etime of your purchase. 2010 Toyota Highlander Offer
If you GO HERE and change your location to where you are, then can view deals on the various vehicles offered by Toyota. It's actually a great site to watch every once in a while for those REALLY great deals.