In PA, it would be impossible to do anything, unless you find the last registered owner. When I bought my XP800... we had to trace down the last owner, because the girl I bought it from, never put it in her name, and the paperwork was messed up. Lucky... we found an old phone #, who got us his folks... and they got in touch with him for me. He was in Germany working, but the local registration shop was willing to do the paperwork as long as I got his signature on the forms, and a copy of his military ID.
It was a pain... but I wanted the 800.
Now... the loophole would be to register it in a state that doesn't need a title to get a registration... then bring it back into your state.