Benjamin Mendy tagged himself at the Hong Kong airport in an Instagram story on Friday morning.
Guardiola added: "Wow I didn't know that". I didn't know it. F--, he's a lucky guy! Before he said he was going one day to Paris, but Hong Kong is far away.
"His injury is not easy, meniscus external, and it's not easy", Guardiola said. "You have to know!" to which the club official said he didn't.
Meanwhile, Guardiola says he has been impressed with Maurizio Sarri's impact since taking the reins at Chelsea in the summer.
Mendy, who joined City from Monaco in 2017, later revealed on Twitter he did not in fact take an unauthorised trip to the Far East - he had just been playing a prank.
Social media funnyman Benjamin Mendy (also a professional footballer) appeared to have been in hot water with his manager for a short while on Friday. Now sidelined with a knee injury, Mendy posted a video in which he tagged himself as being at Hong Kong International Airport.
Shortly after Guardiola's press conference comments were posted on Twitter, Mendy looked to clarify the situation by explaining that he wasn't actually in Hong Kong and instead had been enjoying a joke with his Uber driver.
Guardiola, however, was caught by surprise when a reporter brought this to his attention, but appeared to see the amusing side.
Back in August, Guardiola suggested that Mendy should tone down his social media use, saying: 'Mendy has a lot of things to improve and hopefully we can convince him to forget a little bit the social media and improve a few things'.
'It's a final for us, and we have to play it in that way, ' he said. So in the dressing room, everywhere, I don't pick up my phone.