"Just a usual night, finished work, go to sit upstairs on the train and then...ok apparently not sitting upstairs," he wrote.
The train continued to run, but Mateer said station staff asked him to move to another train car before closing off the area to other passengers.
"I was just bewildered that anyone would go to that sort of length for something so insignificant," he said.
No video was available from inside the train car, but police are searching for three people after reviewing security footage from the station.
"Those who think they're getting away with this behavior, they're wrong," Transport Minister Andrew Constance said.
Rob Mason of NSW Trains called the incident an act of "deliberate vandalism."
"It's really infuriating," he said. "It's no fun at all, people may think this is fun but it's not."
