Asked if it would be OK if Mendy was in Hong Kong, Guardiola said: "Hong Kong, definitely not".
Benjamin Mendy insisted that he was not in Hong Kong after his an Instagram post showing his location.
If Guardiola had hoped to maintain a low profile before City's title challenge faces another serious test at home to Chelsea tomorrow, it did not really go according to plan. I didn't know it. F***, he's a lucky guy. 'I don't know. I have to understand Instagram.
Asking the press officer next to him, Guardiola said, "Did you know?"
"Yesterday he was in Barcelona!"
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.
He said: "I was joking with my Uber driver".
Pep Guardiola was moved to use an expletive on live television when he suddenly became unsure of Benjamin Mendy's whereabouts on Friday afternoon.
The 24-year-old is now sidelined with a knee injury and Guardiola confirmed in his pre-match press conference ahead of Manchester City's game with Chelsea on Sunday that the World Cup victor would not be involved in the game.
His fellow City full back Kyle Walker also got in on the act, taking a lighthearted dig at his teammate for not being in training. The City boss confirmed that Mendy will miss the Chelsea game as he recovers from his latest knee problem.
Guardiola, who praised Sarri's work at Napoli when City met the Italian side in the Champions League last season, says he could see a different Chelsea as far back as August in the Community Shield.
So, it seems like Mendy might be okay with his manager.
However, the situation was cleared up by Mendy shortly after, but via his Twitter account this time.
'It's a final for us, and we have to play it in that way, ' he said. The manager is the manager.