If the ship was British registered, then in 1850 there was no requirement to register a death on board. (That was only introduced in 1854). Death registration only started in Ireland in 1864 so there's no question of it being registered here. Perhaps if the ship was a US vessel there might have been a requirement to register it. (I don't know enough about US law to answer that). But I suspect the answer to your question may be that it wasn't registered anywhere.