Ok so i have lots of objects in a layer and i duplicated the object but i accidently clicked off and now i can't select it anymore...because when ever i click, i select somthing in front which is not what i want.

How do select something that is behind many layers?

You may find it easier to select the object in outline mode (View -> Display mode -> Outline). Or you could select one object and then keep hitting the tab key until the correct one is selected.

If you hold the Alt key while you select, the first time you click it will select the top object, but if you keep clicking, it will start selecting objects underneath, from top of the z-order down.