A few years ago, I spotted a parked car that I had bought new and then sold after 10 years. I left a note under a wiper, but got no reply. Then months later, got a call from the current owner. He confessed that my note freaked him out a little at the time (all I said was that I had bought it new, owned for next 10 years and had a lot of original documents if they wanted them) in case there was some other reason I was trying to get in contact. His girlfriend convinced him to call eventually, we met up and swapped ownership stories and I gave him a box full of receipts, sales docs etc.
So, my point is, the owner that bought from the Iowa dealer may suspect there is some subterfuge, maybe a title issue, divorce dispute or some other problem. I would mail a letter to the dealer, explaining your reasons for trying to contact the current owner, and ask them to forward it to the current owner. Then they can consider your reasons and may reach out.
If it's gone overseas since, another story. But if it sold for anywhere near the $70k figure, it's probably nicely restored and could be in a collection, hence why not registered these last few years.
