It's ridiculous they could keep Fai's involvement a secret. The whole enemy army was destroyed and the hero feated. Plenty of people saw Fai, and the maid, walk to the battlefield. There must have also been soldiers on the walls and in towers who saw at least a part of the fight. Obviously the whole population of the city would like to know how and why they were saved. One or more of the soldiers would absolutely talk (even if it took beer and booze to loosen their tongues). If the author really wanted to make this work, Fai should have walked to the battlefield in disguise, pretending to be a hero from a whatever suitable place in that world, under a fake name. He didn't do that, so it would be a huge plot hole for the news not to spread.