This happened to me recently with much happier results (they found my gear).
Since then, I ALWAYS make sure to INFLATE my BC before I leave it. That way when the rogue wave hits, or the bungee pops off (which is what happened to me), you can just pull it from the surf with NO ONE getting wet.
As for who is liable: everyone one is different. I would approach the boat owner and see if they will accept responsibility for it. Common sense says that when they took it OUT of your hands, they assumed responsibility for it.
Since then, I ALWAYS make sure to INFLATE my BC before I leave it. That way when the rogue wave hits, or the bungee pops off (which is what happened to me), you can just pull it from the surf with NO ONE getting wet.
As for who is liable: everyone one is different. I would approach the boat owner and see if they will accept responsibility for it. Common sense says that when they took it OUT of your hands, they assumed responsibility for it.