Cars.com has some suggestions about trade-ins. It was good that you could walk away.

I just bought a used 2002 EX v6 (43000) loaded in perfect condition for $16,000 out the door after taxes from a honda dealership and the private party value in was $16,500 before taxes. They had a bunch of used Hondas in stock but are not selling them off. That value may be the auction price that was given for your vehicle.

Email and call dealerships around your area and see what they will offer for your car, then take their offer to your dealership and make them match their offer.