Consider: Secret Service is there only in a protective capacity. Due to 4th amendment protections, a search warrant is required to obtain evidence which incriminates the residents of 1600 Pennsylvania Ave and grounds. Since it is was found without a warrant, it cannot be used against the Biden’s. Anyone else, though, is fair game.
It stands to reason that since no one else is being accused, it likely belongs to a Biden. And since they cannot just come out and say this, it is being swept under the rug. It also is not admissible as evidence against Hunter in his diversion plea.