The Exotic version of Black Hammer which dropped during the Daily Heroic yesterday in Destiny: The Taken King is gone. That’s because it was only available for the Daily, in case you missed that part.
According to Bungie designer Rob Engeln, the Black Spindle will be put on rotation, so this wasn’t a one off. You’ll get your chance again.
Per Engeln’s tweets (thanks, reddit), this particular Daily Heroic story mission will come up frequently in said rotation.
Destiny players should always participate in these Dailies because there could be something else just as interesting tucked in there someplace.
According to Destiny Dailies, today’s Daily Heroic is Outbound Signal, where you will need to track a signal from being broadcast from the Dreadnaught and stop said transmission.