Instead of letting the play continue on, there was nothing stopping Cummins from blowing his whistle once he was made aware of his stuff up and take the play back to where the previous play-the-ball was carried out.
From the rule book:
2019 EDITION
NRL
RUGBY LEAGUE LAWS OF THE GAME
INTERNATIONAL LEVEL
WITH
NOTES ON THE LAWS
AND
NRL TELSTRA PREMIERSHIP
INTERPRETATIONS
(APPROVED BY THE AUSTRALIAN RUGBY LEAGUE COMMISSION)
OFFICIAL
FEBRUARY 2019
https://www.playrugbyleague.com/media/3114/arl-rules-book-2019.pdf
Section 17. Referee's Signals
Page 48
Play-the-ball
30. Count of tackle is cancelled and starts again. Wave
clenched fist from side to side above head.
Section 16. Duties of Referees and Touch Judges
Page 42
Changing decision
9. The Referee judges on matters of fact and shall not
subsequently alter those judgments. He may cancel
any decision made if prior foul play of which he had
no knowledge is reported to him by a Touch Judge
Page 43
When to blow
8.1 The Referee must carry a whistle which he shall blow
whistle to commence and terminate each half of the game.
Except for these occasions the blowing of the
whistle shall temporarily stop the play. The Referee
shall blow the whistle:
(g) when a stoppage is necessary in order to enforce
the Laws or for any other reason.