Like everyone else, I got mine last Thursday (11/7), and instantly used it to preorder Metroidrime (which also comes with a $10 digital coupon) for effectively $14.99!
I would contact them, but emails with BB sometimes go quite slow (for responses), so I usually call them with better results (hold times are often not long - at least when I call them). Good luck, I hope you get your coupon!
Do you have a bulk mail folder? Check there. BestBuy is notorious for flagging their coupons as bulk mail (while their ads mysteriously are flagged as real mail) in the hopes that you will delete it and not get to use it (as is what happened to me with the $10 coupon with LOTR).
Check your bulk mail (if you haven't emptied it in the past few days)...it should be in there.