The dealer blew a perfectly good chance to really get some tremendous advertising, imho. Of course, they'd have to print a notice that no coupons printed before a certain date would be accepted in the future, one coupon per purchase, expiration dates, and all that fine print on subsequent coupons, and run it with their new coupon deal as the story broke in the local news....
A few years back, someone dug an old coupon for a $19.99 Earl Scheib's paint job out of some yellowing publication which had no expiration date on it. They honored the coupon and painted the guy's car for $19,99. The press they got was likely worth multiples of what they lost on that one paint job.
Why would I buy a car from a dealer (that I otherwise wouldn't have) because he gave someone that I don't’ know a free car, because she brought in some yellow paper? I think I'd go to a dealer that could still afford to cut me a deal.
I presume you don't own a car dealership.