Sinister Motives, Miles, and Gwen: When an encounter card is added to my deck, do I have to re-sleeve that card to match my player cards.

No, encounter cards added to player decks are done so as is. Additionally, there is no requirement for players to treat the encounter card backs within their decks as hidden information, meaning players may (and are encouraged to) anticipate when an encounter card will be drawn from their decks and prepare accordingly.

– Sinister Motives rulebook