The dice, then, are the agents of chance and fate, not an arbitrary rules system that changes depending on who's adjudicating the action. Dramatic fear and uncertainty come from using the rules wisely in conjunction with the situations created by the Storyteller.
the Storyteller could […] rewarding the players' characters with the envelope-clue at the conclusion of some other challenge — say, among the belongings of a ghoul they overpower or in the library of the Primogen while they're snooping around her haven.
You’re the arbiter of what works best in your game — mutually determined in play with the storyteller and other players — and you’re free to use, alter, abuse or ignore these rules at your leisure.