Maybe this will stop the insanity here:
What are your procedures for processing a stop payment request for a cashiers check purchased by your customer, made payable to another entity, the check is lost in the mail...who has the right to place a stop on the check? Now one step further, if the payee signed a registered letter, is ...
www.bankersonline.com
Again, I don't post these things with glee or any enjoyment for the OP's predicament, it really sucks and I'm emphathetic. But ranting about hire a lawyer and the bank is at fault is completely misguided IMHO.
Work with LEO and hopefully this dirtbag gets caught. Good / painful lesson for others buying a used vehicle to not fall into a similar trap.