Hi, 

Yes, that's exactly what I am referring to. You are right that the card comes from discard pile, but it has been ruled that cards revealed from the discard pile of the encounter deck count as cards revealed from the encounter deck: 

11 – Spider-Man’s enhanced spider sense says ‘When a treachery is revealed from the encounter deck cancel its when revealed effects.’ however Adam Warlocks Cosmic Ward says ‘when you reveal a treachery card, cancel its when revealed effects and discard it…’ Is there a intentional distinction on these cards as to where the treachery card is revealed from? For example, in the Mysterio scenario there are encounter cards that are shuffled into your player deck. Are these cards not considered to be revealed from the encounter deck and if so does that mean Spider-Man can not cancel them?
There is also ‘Return the Favour; that player card discards cards from the encounter deck until a treachery is discarded. You then reveal that treachery and deal 5 damage to an enemy. You have to reveal a treachery as a cost to play the card, however the rules reference states you still consider a treachery to be revealed even if you cancel its effects so I believe you can cancel the treachery card.
However, when you reveal the treachery it is already in the discard pile so it appears to be being revealed from the discard pile, not from the encounter deck, so does this mean Spider-Man can’t cancel it because he can only cancel treachery cards that are revealed from the encounter deck but Warlock can since he can cancel any treachery which is revealed?
Sorry but if I were to cancel the effects of a treachery which was revealed due to playing “Return the Favour” would I still be able to resolve the effect of “Return the Favour’ and deal 5 damage? My understanding is that revealing the treachery is part of the cost to play “Return the favour” but treachery cards are still considered revealed even if their effects are cancelled, so I could cancel the effects of the treachery and still deal the 5 damage. Is this correct? Some cards like “Enhanced Spider sense” only cancel when revealed effects while other cards like “warp reality” cancel all the effects of the treachery. Could either of these cards be comboed with “return the favour” so I can cancel the effects of the treachery and still deal the damage?

Our ruling for this is, Enhanced Spider-Sense should work just like Cosmic Ward does: when a treachery card is revealed, cancel its “when revealed” effects. Additionally, encounter cards can be thought of as being “from the encounter deck”, even if the method of which they were dealt to you was not directly from the encounter deck (such as in Mysterio’s scenario). Similarly, for Return the Favor, the revealed treachery card should be considered as having come from the encounter deck.

Thanks in advance!