Custody of resources (especially during transfers and transportation)

How about we generally assume (without bothering to document) that vf:Owner has custody of a resource, unless custody is formally delegated to someone else?

(For instance, an Owner giving custody of a resource to a delivery service, and then transferring ownership to a new owner/ buyer upon the signing of a receipt of delivery-- implicitly terminating the temporary custody of the delivery service).

(Or, a moving company assumes custody of a piece of furniture while transporting it to a new location, without ownership ever changing.)