Do you have a link to the Starbucks offer you mention? I don't know whether or not they do this by us. I've never heard of this before (and my brother worked there for three years, only leaving this past August). Not sure where else to check.
I don't have any link, but I'm pretty sure this offer is on every Starbucks bag nationwide. You can always check a bag at your local supermarket and ask at your local Starbucks. It seems to me that if they have a coupon at your local market, they would have to honor it, by law.
The star codes are for if you're a member of their rewards program. Earn 30 stars and you're a gold member, which means for every 12 stars thereafter, you get a free drink. And if you're a member you get a free drink on your birthday.