How was it inconvinient for yacht owner? I have such yachts and some houses that I myself at times have had to take in or delete piece by piece as the hud was not working due to something or it had timed out or I had taken in the rezz box so I could not derezz the whole thing at once.
One time I had rezzed a small furnished skybox over someones water and they started returning it to my inventory piece by piece, was it a problem for me or did I have to put it back together piece by piece, no, just rezz the box and click and voila, not just that all the parts went to lost and found folder, simply delete that or just let it be, so she was the one inconvinienced all she had to do was to tell me to go trough the hassle of removing it, which again would be piece by piece if hud or rezz box wouldnt do it as a whole. Even auto-return sends such things back piece by piece.
More than likely the yacht owner got logged off while sailing and the boat continued till it landed at your place on its own, I saw this happen a few days back, usually they get auto-returned, you should set that up too.