sounds like a enemy destroyed it whild ur underway...
if its not that long ur buildingparts should be close were the ship was last seen...
if not build a raft if no materials availible drunk urself, and respawn in the bed, or if no bed a the ritual place.. build a new boat and catch the corps...

lesson nr1 never leave ur ship alon in a place u dont know, if u go ashore use a close by isle, never go on land on the main landmass, allways keep distance or if u do stay close and eyball ur boat, they attack it as long ur in the Proximity if u leave they stop...