Down by four points early in the second half, Storm left winger Xavier Coates batted back a towering bomb into the hands of teammate Howarth.
The centre was mobbed by Panthers defenders as he attempted to burrow over and referee Ashley Klein said he had been held up in-goal by Izack Tago and Dylan Edwards on Penrith's right edge.
Howarth's effort was sent for review by bunker official Grant Atkins, who supported the on-field decision of no-try.
Screenshots circulated on social media appeared to show Howarth had grounded the ball, but vision shown to the media by NRL head of football Graham Annesley in the bowels of Accor Stadium showed Klein and Atkins had made the correct call.
Annesley showed frame-by-frame replays of the footage which revealed that at no point did Howarth ground the ball.
"When I saw it live I was saying what everyone else was saying, I thought I saw the ball on the ground," Annesley said.
"It's only when we go back and look at it clearly that you can see the different colour between the arm and the ball.
"The ball is sitting on top of the arm, which then gets lifted up.
"They (the bunker officials) are looking at this over and over again before they announce their decision while we generally have one replay.
"We don't have time to clinically examine it like this but the bottom line is that the decision was correct."
It was to be the closest Melbourne came to snatching back the lead, and midway through Sunday night's second half, the Panthers made it a two-score margin.
Paul Alamoti dived over on the right following a Nathan Cleary bomb that was picked out of Will Warbrick's hands by Liam Martin to help Penrith seal victory.
