i think wulfie's right. the fact is that sometimes it's just bad luck.
37mm is a lot of gun and most planes do go down with just a couple hits, but consider the locations of the hits and the corrections the pilot could take. you take out an engine and hit a wing (im assuming the outer section) and you're looking at the pilot adding opposite rudder and nursing the airplane to what probably ended up as an unsuccessful ditch. bombers are tough airplanes, and the c47 is a bad comparison because it's converted from civil...i put one down with 6 20mm cannon shells out of an LA7 once because i snagged him in the wing root, they're flimsy. and what's the big deal about it anyway? wasn't your objective to make him break off? you even got credit for the kill!
be happy, from the looks of this forum it doesn't seem like it happens very often. wulfie's right, it "could" have survived, and it did.