Maffeo, 20, is on a season-long loan at newly-promoted Girona, who are also owned by the City Football Group.
The Spaniard made 27 appearances for Girona last season as they secured promotion to La Liga for the first time in their history and Maffeo was quizzed by five-time Ballon d'Or winner Messi during Saturday's clash at Estadi Municipal de Montilivi.
"He [Messi] asked me a couple of things, like if I was loaned by City and how old I was," Maffeo said.
"It was all good."
On Messi, Maffeo added: "I had to mark him and I had to be close to him and not watch the ball.
"It is difficult, not just from a football perspective, but also psychologically.
"I appreciate the trust the coach placed in me."
Girona are 16th in the standings, 13 points adrift of high-flying Barca after six matches.