A friend bought a boat from someone that had
lost the title, and they had to have the state do a title search. I would assume you'll need to do something similar.
If it was sailing around the world, it might be coast guard documented. You'll need to find the HIN (hull identification number) on the boat. Ours is in our
engine compartment, but maybe someone can comment on where it is in an
Island Packet.
If it's coast guard documented, this may help:
https://cgmix.uscg.mil/psix/psixsearch.aspx