Exotics will drop from any yellow bar chest, Random Hive, Fallen or Cabal chest (not the location chests the actual enemy faction chests like the mouldy Hive chests on Titan) and public event chests. What you experienced was simply a drop from a chest. As far as I am aware exotics have never dropped from an actual enemy kill and can't. It's not even in their drop table hence why the 3oC description says from doing location events. Shooting random enemies is not an event and doesn't count as one. Edit: To be clear I was told by a rep when getting a refund for a friend for D2, that they were about to remove it from sale until the issue could be resolved so clearly the rep had at some point been told this may be happening. So don't think for a moment that Bungie have been acting of their own volition when fixing these issues. If they had their way they would simply print a screenshot of the team all flipping you the bird while throwing dollar bills in the air and making it rain!