Neuro Vault: Played straight. Only the old-time classical version, though, where you hide it in people’s memories using good old-fashioned memory palace techniques, or closely related gnostic overlays emulating them. The trouble with imprinting stuff on bits of the brain that aren’t the usual memory regions is that it tends to show up as a pretty clear anomaly on a mind-scan, if anyone cares to look, unless your courier is already going to be drawing attention to themselves by virtue of exotic and unusual mental architecture.