Guardiola, who was speaking at his press conference ahead of facing Chelsea at the Etihad Stadium on Sunday, was informed by a journalist that Mendy - who remains sidelined through injury - appeared to be in Hong Kong, judging by a post on his Instagram Story.
“Wow, I didn't know," was Guardiola's rather stunned reply, which was being broadcast live on Sky Sports News.
"F***, he's a lucky guy. He said he was going to Paris but Hong Kong is far away, I need to download an Instagram account.
“Yesterday he was in Barcelona . It will definitely not be OK if he is in Hong Kong."
But Mendy later responded on Twitter , saying that he had tagged himself in Hong Kong as a joke.