I received a letter years ago seeking title for my first car. Guy I sold it to never transferred it and someone else in another state ended up with it. Duplicate title for $20, postage, done. I'd probably send a letter with a picture in current state, explain you want to restore it and use it or whatever you'd do with it and ask for a signed duplicate title which you'll compensate him for any fees. Ask for a call back. He may help, or if he wants it back it's not a big deal as there are very few uses for a bare frame with no title anyhow. I'd never put any time or money into a frame that the government could steal from me at any time with no recourse.