To earn the Smoke Detector medal in the Search and Destroy campaign, I have to
Use the Smoke Pellet to create a smoke cloud and take down a henchman as he panics in the smoke.
I've hit ← twice on the D-pad to select the smoke pellet, but pressing L1 throws the batarang. Holding down L1 doesn't seem to work either. How do I use the smoke pellet? Is it a future gadget upgrade?