Most states require that the seller disclose mechanical problems with vehicles for sale prior to the sale. The seller would have to disclose the problem and sell the vehicle to you as is, but you would have been under notice. If there were no problems disclosed to you at the time of offer and you were not given notice of sell as is, you may have some recourse. I would consult with an attorney who knows about automobile resale business in your state/county. Transmissions do not fail overnight unless there was an electrical failure of a sensor or connection which would cause some of these problems. But if it is mechanical, the ATX fluid would be brown, bad smell etc...If the fluid is new or has additives, there is your evidence that the seller was probably with-holding information from you. Try checking your battery connections to make sure the guy did not switch batteries on you over night and left a terminal loose. Any other actions will probably cost you money and you will have to determine what's best for you with your attorneys' advice.
