Resources.Load(filename) as Sprite is returning null

The path-name is correct.

public var pic : Sprite;

function Start(){
    pic = Resources.Load("Targets/1") as Sprite;            //pic becomes null 

“1” is not a very descriptive filename; If I had to take a shot in the dark, do you happen to have two resources with the same name but different extensions? (a “1.png” and a “1.prefab”, for example?) - Resources.Load won’t know which to pick and so will return null in that case.
I’d recommend you give your resources more descriptive names.

Try using the generic overload: Resources.Load<Sprite>("name")