There is no way to get targeted for the promo if you were not. (Leaving aside whether you might 'slip by' someone at Starwood empowered to add the code when they shouldn't as discussed above.)

What you COULD do is contact the Amex corporate offices. They can't add the code. But they could compensate you with the # of Starwood points that you would have saved via this promo. They might be inclined to do it if you're a good customer.

(See for instance the discussions here and in the Amex forum on contacting these folks when you're not targeted for the 50% bonus on spending or double points on spending above a certain threshold. This year I was given a large number of points PLUS the points I would have earned from the 50% bonus promo. But I wasn't technically added to the promo. But Amex was looking at both heavy spend on the Starwood card and on my Amex Plat as well.)