I thought we had it in the bag, but Kawhi missing that free throw isn't what ruined it IMO. Parker and Danny Green had a 2 on 1 situation against Ray Allen at one crucial point, and instead of passing the ball to Danny Green, Parker opted to hold it, prompting Allen to coral him and purposefully foul him. Sadly, Parker did in fact go 1 of 2 at the line during that session.
I think that's what killed it. That and Pop leaving Timmy on the bench when Bron went for the hero 3 shot and missed, only to have Bosh rebound it. The rest...well, we all know.