Sorry... the dealer is right in this case. It's a dealer trade vehicle. The selling dealer has absolutely no control over the stocking dealer selling the car to someone else before the deal is finalized. The selling dealer does not contract with another dealer for a dealer trade until he has a signed contract and check in hand. And the stocking dealer is not going to lose a sale just because he has had an inquiry about stock. That's just normal practice in the new car sales business. It would be completely different if the selling dealer had the car in stock at the time you signed the order. As it is, it's just bad luck and the dealer is not liable to you for anything - the maintenance plan offer was merely a goodwill gesture. You might be able to get the dealer to extend a little more goodwill and maybe find a similar car that has an extra option or two to sell you at a price close to what you negotiated. But they don't have to do that (or anything at all really) so it would be best not to aggravate them too much lest they tell you to go away.
You could contact Ford Customer service and see if they will extend the $750 coupon expiry date based on a sale waiting on delivery (if you order the car you want). Or you can request multiple additional brochures using different email addresses - most people have good luck doing that. The rebates will still be around... maybe not exactly the same but there will be rebates.
2011 Pony Pkg. convertible M6
Am WS7 (sold)