The car dealer is required by the purchase contract to return to you all consideration (i.e., everything) given for the purchase, included your trade-in vehicle. If you gave a $2,000 down payment and a car as a trade-in, the car dealer must give you back both the $2,000 and the trade-in when you return the car you purchased.
There may be times when your car dealer may tell you that it already sold your trade-in, and you can be offered the value of the trade -in as listed on the purchase contract. On the other hand the language of the purchase contract does not appear to give the car dealer this option. The return of the trade-in, thus, is being required. However, if the car dealer does sell your trade-in, at the very least, you should tell the car dealer that it has to give you whatever is the highest value for your trade-in out of either (1) the value of the trade-in as listed on the purchase contract, (2) the fair market value, or (3) what the car dealer received when it sold your trade-in.

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