Various national laws and international law create a very complicated situation in regard to jettisoned cargo, abandoned ships, salvage, etc. The question of who has a right to claim such things is also complicated by insurance considerations, as an insurer has an interest. One of the things I do know is that no one wants to leave a ship, still afloat, abandoned; if so, the first person to put a cable on board it can claim it as its salvor. Hence there will always be an effort made to get some member of the crew to stay on board an otherwise abandoned craft as long as possible to allow the owners to get their own salvors to it and thus preserve their ownership. But in all cases of cargo, stores, vessels, etc. the law is extremely complex and an ordinary lawyer isn't likely to know much, if anything, about it -- it's the province of a specialist, the admiralty lawyer.
