Try looking for the VIN stamped on the tongue.
It may be difficult to track the old title down if you don't have the seller info. Motor vehicle law varies from state to state. If you can locate the last registered owner you may be able to have him fill out an affidavit of sale. You may have to post an assurity bond to cover any possible old liens and do a motor vehicle search to make sure the trailer is not stolen.
Be ready to spend some time at motor vehicles. It has been my experience that if one DMV clerk gives you an answer you don't like, get on a different line and you will get a different answer. There are businesses that will do this for you, but based on your description may not be worth the cost
Sail on silver girl. Sail on by. Your time has come to shine.