It's Not Over Until Your Hear The Call
Two nights ago Chicago White Sox catcher Tyler Flowers broke one of the cardinal rules of catching - He assumed that a call had been made and abandoned the play before hearing the umpire shout "OUT!".
If you haven't heard a call, there's a good chance one hasn't been made and the runner is not yet out.
Catchers, until you hear a call being made your job it to continue to pursue the runner with the tag. Otherwise, you risk being in an unfortunate situation like Flowers was on Tuesday. The runner looked like he was indeed out, but that is not the catcher's call to make. Our job it to make sure that the tag is applied until we hear the call from the umpire.
Flowers had a ton of time to re-apply the tag, but he gave up on the play because he assumed a call had been made and instead turned his head up to the umpire while the runner slid back in to score the run.
Even if you think you tagged the runner out, if you haven't heard a call you must continue to apply the tag.