A post-race hearing promoted Hamilton from fourth to third after Trulli was penalised for passing the Englishman while the safety car was out.
Trulli and Toyota have been reinstated to third place.
The Italian was initially handed a 25-second penalty for the incident which saw him demoted to 12th.
Hamilton was summoned by stewards on Thursday to discuss what the FIA, motorsport’s governing body, described as "a new element" of evidence.
It was not clear what the new evidence was, although it was thought to involve pit-to-car radio conversations between the team and driver, with the FIA ruling that there had been a breach of the international sporting code
The yellow safety flags came out at Melbourne after a collision between Red Bull’s Sebastian Vettel and Robert Kubica in his BMW Sauber.
Trulli slid off the track and was passed by Hamilton but the Toyota driver said he had little choice but to overtake the Briton again.
"When the safety car came out towards the end of the race, Hamilton passed me but soon after he suddenly slowed down and pulled over to the side of the road," he said.
"I thought he had a problem so I overtook him as there was nothing else I could do."
Hamilton had told Speed TV after the race that Trulli went wide onto the grass at the second to last corner.
"I was forced to go by. I slowed down as much as I could. I was told to let him back past, I don’t know if that’s the regulations, and if it isn’t, then I should have really had third," said the Briton.
Toyota had said after the race that they would make a protest but dropped that on Wednesday because they felt it had no chance of succeeding. BBC