Depends on what capabilities I have regarding placing the duck. If I'm able to make pop out of thin air, I would spike it on the end of Joab's spear just before it hit Absalom. Thus, it would have spared Absalom, avoided alienating Joab from David further (if I recall correctly, things were already tense between the two of them), and, yes would have caused much confusion over the soft, saffron-colored bird-shaped statuette that makes a loud, piercing noise when squeezed that somehow ended up on the end of Joab's spear. It might've also made a loud squeak when it hit Absalom, adding to comedic effect. If, however, I have to place it by hand, I would go into a pagan temple, and discreetly replace one of the smaller idols with the duck. I would then hide until the priests came in, and watch hilarity and chaos ensue as they try to determine the meaning of this omen. I would then bring the idol back to present times, and donate it to an archeological institution.