The Czech stopper went down midway through the second half of Wednesday’s 0-0 Edinburgh derby draw at Tynecastle.
TV cameras appeared to show a couple of Hibs fans reaching out to strike Zlamal before he went down. He was able to quickly recover and finish the game.
The 32-year-old took to social media on the morning after the match, thanking the support of what he described as “real fans” while condemning the troublemakers.
He wrote: “Yesterday’s result was 0-0, but everybody knows who the losers are. You punched me in the face. I was ok - no big deal, but feel sorry for your personal tragedies that force you to behave like this.
“Our kids are watching the games and I’m sure they can recognise their real heroes.
“I’m grateful for who I am and what I do for a living. Thank you real fans of sport and football.”
In a bad tempered affair, Hibs boss Neil Lennon was also the victim of fan violence when he was struck with a coin thrown from the Tynecastle main stand.