The six-time world champion, who has championed the race-based push for social justice inside Formula 1 this season, was conspicuously absent when the rest of the drivers gathered on the Italian GP grid.
Sebastian Vettel was also absent.
"It was about the timing," Finland's MTV quotes Hamilton as explaining.
"I had gone back to my garage, which is the furthest away. I tried to make it back with a scooter, but I just ran out of time.
"Normally I know very well how much time I have to go somewhere, but when I got to the garage they said I should go back. And when I got there, everyone was already there," Hamilton added.
However, the Mercedes driver played down the significance of his absence, even though he has been critical even of those who choose to stand rather than kneel for the drivers' anti-racism display.
"Yes, I missed the kneeling, but it's not the end of the world," he insisted. "I saw my whole team kneeling down, which was great to see.
"Maybe next time I won't go all the way to my garage, especially if it's a long way. Usually there is a toilet somewhere that is closer."
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