A dealer may accept return of the vehicle in exchange for a coupon toward purchase of a later model vehicle, without any written documents explaining the reason for the return. Or, in a lease situation, the lemon may be returned for an undisclosed amount of credit simply churned into the terms of a new lease. The real nature of these buybacks may be best explained when your attorney introduces testimony of the vehicle's previous owner. Whether this defense will work depends on the language of a particular state statute. Also, some lemon laundering statutes clearly apply to such voluntary agreements to take a car back.
Most laws are somewhere in between.
No matter what legalistic argument a manufacturer wants to make, it's still misleading under a state deceptive practices statute to fail to disclose defects so serious that the manufacturer actually took back the car. Tax breaks Manufacturers sometimes trip themselves up while trying to avoid lemon-laundering rules. This ruse is fraudulent if a court or IDM panel ordered the buyback. Work with an experienced lawyer in your state.