Prismatic Lens will only swap costs if the drawn minion and the drawn spell end up in your hand. Other cases where Prismatic Lens won't fully resolve include playing it without any spells remaining in your deck, and playing it with 10 cards in hand causing the minion to be drawn and the spell to be burned. We like this as a rule, but we're open to discussing a change.
Josh Durica
Prismatic Lens will only swap costs if the drawn minion and the drawn spell end up in your hand. Other cases where Prismatic Lens won't fully resolve include playing it without any spells remaining in your deck, and playing it with 10 cards in hand causing the minion to be drawn and the spell to be burned. We like this as a rule, but we're open to discussing a change.