Well you didn't give a lot of details but I have to ask why are you asking the seller for a title to "your" trailer? I'm guessing that you have not transferred the title of the trailer into your name and you have lost the title that the seller signed over to you? If that is the case what exactly do you think the Missouri DMV can do for you? As far as they would be concerned the trailer still belongs to the seller and is still registered in Illinois. Bottom line you have to find the seller, the Missouri DMV isn't going to do that for you. They gave you the only advice they can give you.