I dont know on a C4...but on a C3 you dont have to drop the tank...you can reach around the tank to retrieve it. If you know the build sheet was placed on top of the tank on the C4, then it would be worth-while to try to reach it.
And no, I would not suggest getting a copy from the NCM if you have the original sitting on your tank.....other than that, there is no other way to get a build sheet