I have read through this thread a couple of times... It sound like what was signed was a sales contract... A contract by definition is a promise for a consideration. If the OP gave the dealership a $10,000 dollar check as a deposit that is only done to bind a sales contract. Never done for a sales proposal.
The only recourse the OP has is a reliance on any buyer remorse statues or regulations...
While doing a stop payment on a check is an option it may well be too late and if there is a signed contract open up legal remedies for the dealer. The OP would be best served to follow the advise of a legal professional who has complete knowledge of the transaction and the statues and regulations governing.
The dealer is not going to have any incentive to void the deal unless legally compelled to do so... An attorney is the best option for the OP... Time is of the essence...
The motivation for buyers remorse is not a factor in any statute or regulation I am familiar with nor part of most dealership business plans... So in terms of voiding the deal what its going to come down to is what the dealer is compelled to do...
