I just want to make sure I'm reading and understanding this correctly.
You have a triple channel kit of DDR3 RAM, but only have 2 sticks of it due to misplacing the third stick? The other 2 sticks should work just fine. A triple channel kit just means that it is made up of 3 sticks of memory matched for performance. Each stick will run individually, and the 2 will run together, but the computer will not be running in triple channel mode.