[stir]

Since you are new to this, I'm guessing you did not have a read on the CO, however if you felt he was likely to bet the flop, I would check the flop, then c/r after he bets as a semi-bluff in hopes a getting the free card on the turn.

Other comment is there is no way you should have called the river as weak as your hand was; you are overly concerned about a bluff. In my experience bluffs will occur on the flop and turn, or as a blind steal. They are infrequent on the river unless you are dealing with a maniac.