Jets coach Gary van Egmond attempted to raise the matter with the fourth official during the game and mentioned it in the post-match press conference, questioning match officials' ability to enforce the ban.
Arnold was banished to the stands for abusing officials in the round 16 draw with Melbourne Victory and Van Egmond became suspicious when he noticed Mariners assistant coach Phil Moss and goalkeeping coach John Crawley on the sideline communicating with a third party via an earpiece.
"The rules are the rules ... if I was the fourth official and I saw one of the assistant coaches with an earpiece and a walkie talkie and, you know, the coach isn't actually on the bench, what would you think?" Van Egmond said.
For much of the first half Arnold was in the private box of stadium lease-holder John Singleton while assistant Moss called the shots. The former Australia coach later moved to sit on his own.
Moss denied any contact with Arnold in the post-match press conference, saying he was instead speaking with midfielder Adriano Pellegrino, who was the Mariners' designated eyes in the stand and the Mariners repeated those assertions on Sunday.
"There was no contact between Graham Arnold and the sideline," a club official said.
"It is not the first time we have used someone to read a game up high in the stands ... Patrick Zwaanswijk also did it recently."
An investigation into the matter will result if the incident is mentioned in the match report of the match commissioner or the fourth official, which is lodged on Monday, or the Jets make an official complaint.
If Arnold is hauled before the league, sanctions would include a further, lengthier ban and a hefty fine.
"FFA will wait for the reports of the match commissioner and the match officials, which is the normal course in these matters," said an FFA spokesman.
"If the Newcastle Jets wish to make a formal submission that will be
dealt with on its merits, but at this stage FFA has no basis to make any
comment on the speculation about a breach of disciplinary regulations."
Arnold has been sailing close to the wind for a little while now.
had a running battle with a Western Sydney fan during his team's 2-0
loss to the Wanderers in round 15 and there were suggestions that he
continued communicating with his bench despite being sent from the field
But it would surprise if he so openly flouted the one-match ban.
accusations were the main talking point in the aftermath of a rather
subdued F3 derby which resulted in the Mariners extending their lead at
the top of the A-League ladder, after both sides failed to make the most
of a series of chances to break the 0-0 deadlock in the final 20