As with a regular will the private & public keys as well as recovery codes if any should be written and given to the trustee or executor of the will. these are the only access points to the investments and even if the owner were alive and lost these his/he investments cannot be recovered. It also provides some security as some wild family member cannot access and run off with the investments like has happened before (knew a guy that cleaned out his parents and vanished for about nine years before he got picked up on radar in another country.).