Who is right here?

Ok so I want some opinions and I know this is my mistake but is this person right to do this. Me and my husband just sold a car since we just bought a new one and didn’t need this car anymore. The car sold very fast and the guy who bought it got a great deal, we weren’t looking to make a bunch of money just to get rid of the car we don’t need and make room in our driveway. We easily could of sold the car for a couple thousand more than we did.

2 days after we sold the car we realized we made a huge mistake. We left a $3000 portable projector in one of the storage compartments under the seat in the car. We haven’t used the projector in months so we forgot it was in there. We left it in there after we used that car to go camping.

I called the guy and explained that we left it in the car and if we could meet him or drive to his house to come pick it up. The guy says since he already purchased the car and that was in the car then it’s his and considered included with the car.

I know there might be nothing I can legally do about this, but it’s frustrating since he knows it wasn’t included in the purchase and was left in the car by mistake. Who is right here?