Rumours online suggest Gyllenhaal became embroiled in a heated moment with the man after approaching him and demanding he delete the picture.
The Hollywood hunk appeared to confirm the news when asked about the incident, telling Entertainment Weekly, "That's true. I think it's an appropriate space to keep privacy. I hope that people wouldn't disagree with me on that."
But his spokesperson insists it didn't happen quite how gossip bloggers have described, amid claims Gyllenhaal had grabbed the man and thrown him against a wall.
His rep tells Eonline.com, "There was no scuffle, it was an excited fan who tried to take his picture in the restroom. He asked the guy to please delete it and he did! No drama."