How were the checks deposited incorrectly? What was your agreement regarding the title? When were you supposed to receive it? At the time of sale? From the bank? Once checks cleared?
You currently have possession of a car you did not pay. You would be well served by contacting an attorney and discussing the situation.
This answer is not legal advice. You should act or refrain from acting based on this answer. This does not form an attorney client relationship between you and Regina Gordon, Esq. Such a relationship is only formed after you sign an engagement agreement.