Sforno on Numbers 5:8/ספורנו על במדבר ה׳:ח׳

1'המושב לה, when the original owner of the stolen property no longer exists, it is proper to make restitution to the “boss” of the person from whom it has been taken, his “boss” being none other than G’d. [The author considers any property owned by any one on earth as only “on loan” from the real owner, from G’d. Ed.] Our sages phrase this as “when the servant dies he has to return it to the master.” (Baba Batra 51)