Why didn't Snicko show spikes despite ball deviation in Yashasvi's dismissal?

Team India opener Yashasvi Jaiswal was given out caught behind by third umpire in India-Australia Boxing Day Test as the ball showed deviation, but Snicko didn't show spikes. The Snicko shows only ambient noise and the ball had grazed Yashasvi's gloves without producing sound. As per experts, only HotSpot could have conclusively resolved the incident.