Am I obligated to pay the expiation again if I appointed someone to deliver it to the needy but did not confirm its delivery?

You must be certain that the agent paid the expiation as due for your responsibility to be cleared. If certainty is unattainable, then strong presumption suffices. So, if you are certain or strongly presume that he paid it, your responsibility is cleared. Otherwise, the default is that you are still liable for it, and you must contact him to confirm, or pay it again to clear your responsibility with certainty.