Card exposed question

[LiveInPeace]

Before the flop, a card is exposed to you just before it goes in the muck. You believe you are the only person to have seen it, and you believe noone else knows you've seen it. You're still in the hand with no current intention of folding.

My question is: do you have an obligation to declare the card you've seen to the rest of the table, or is this information just a bit of good fortune for you?