According to Wiki (I know ...) the Navy struck her off the list and she fell under private ownership as the Lord Sandwich. She was hired by the RN during the Revolutionary War as a troop transport. So, if she was not a commissioned Royal Navy ship, what is Britain’s claim?
Yeah, Lord Sandwich... great, now I want to go to Arby’s.
If they scuttled her, they probably paid off the owner, and the owner was probably glad to get what he could (it had been through some serious damage). In that case, there's an international agreement that military vessels remain the property of the home country, in this case, the UK.