Today I was playing a game and had only my C'Thun on the board and my opponent (a Hunter) played a trap. I figured I was pretty safe as C'Thun would survive a damaging trap and I had an Innervate in my hand if he were to get returned. However, the Freezing Trap returned him to my hand and increased his cost by 2 (to bring it to 12) and when I played Innervate, it did nothing (kept my mana at 10 and did not allow C'Thun to be played).
It seems a bit overpowered for such a low cost trap card to essentially act as both a hard removal AND reduce your hand size by one (because you're then stuck with the useless 12-cost card in your hand), but aside from some sort of "Your minion costs are reduced by two" card, that seems to be the case.
Am I missing something? Is there a better way to defend against this aside from "Play a low cost minion, hope it doesn't die and attack with it first the next turn"?