If they used everything else that they used aside from hot spot, I could say without being conclusive that there was no reason to over turn the decision. In other words, there was nothing glaring to say it was out, the noise appeared scratchy and perhaps after the ball had passed, and with that, it should be given out.
But one has to ask with the use of hot spot conclusively showing NO spot at all, and the slo mo hot spot showing the ball went under and past the pane of the bat, that is absolutely not out. And therefore, if third umpires are to intervene with reviews, hot spot has no relevance at all and should be kept to being a TV gimmick, and nothing more.
Utterly disgraceful third umpiring. Clear as day he wasn't out.