Flown the cooop

I'm feeling very sad. Our duckling and mama flew the coop today. Well mama flew and the duckling went under the fence. They promptly fell into the rain drain down the street. A few phone calls later we saved all but one of the ducklings. I thought the 12th duckling had drowned, but unfortunately, I was wrong. We were just walking past that drain and heard his little tweets. I don't know what to do. He's not going to survive without his mama and she and the other 11 ducklings are gone now. There's no way to find them and get them back together. Do I call animal rescue again, get the workers out here, have someone go down the drain again to save a duckling who has no chance of survival? Or do I let him stay down there till he runs out of food (there's a pipe that is out of the water for him to rest in) and know that he won't be killed by a predator? Sigh, this is a big moral dilemma. I haven't told Sarah that I heard him down there, she would cry as if her heart were breaking and I can't handle that. Hell, I'm crying for this little guy now. There's not really a way to save him, he's a mallard and therefore can't be raised domestically here.
What do I do?