Calculus Affair: Does Arturo Cartoffoli remove the mirror from his car?

Have just re-bought The Calculus Affair, and there's the scene - described by some fans as the funniest in Hergé's Tintin oeuvre - where Arturo Cartoffoli helps Tintin and Captain Haddock give chase in his Lancia coupé.
But something confuses me.
I distinctly remember a frame where the Italian rips off his rear view mirror with the words, "What's behind me doesn't matter".
That frame is not in the edition I've just purchased. Is my memory playing tricks, or was there a change made? Can anyone help?

I'm pretty certain that frame's never been in the book. Some of the Tintin stories had scenes that were in the original versions as first published in Tintin magazine, but which were cut from the subsequent book versions, but I've never seen the frame you describe mentioned or shown in books about Tintin where such scenes have been reproduced. So I'm wondering if it's a moment from one of the animated adaptations of The Calculus Affair which may have morphed into a comic-strip frame in your memory. But I should stress that's just a pure guess as I haven't watched them myself.

I may be misremembering, but I'm not confusing it with any animated adaptation, since I've not seen one of The Calculus Affair.
It's so vivid as a memory - laughed about it with my mother as a young lad. Will have to fish out my battered 1970s originals...

Thanks, though.

Indeed you are - it's not from this book, and it's not even from Hergé.

What you seem to be recalling is a joke from the 1976 movie, The Gumball Rally, about an illegal high-speed road race from coast-to-coast in America.
The remark is made by Raúl Juliá, as the 1972 Ferrari 365 GTS/4 driving Italian lounge-lizard Franco, in an exchange with Tim McIntire as Steve Smith, his team-mate (and not Michael Sarazzin, as I initially remembered).
Franco says: "And now my friend, the first rule of Italian driving–" [Rips the mirror from the Ferrari's windscreen, and throws it out of the car] "–What's behind me is not important!"

Astonishing. I do believe you're right! So I must have been laughing about the Gendarme scene with my mother, all those years ago. Thanks for clearing that one up, Jock