The French title "Les Petits Mouchoirs" refers to an idiomatic expression that is similar to the English term "Sweeping something under the rug". You cover something up with a napkin or a handkerchief and pretend it's no longer there even though everyone knows it is. The English term "Little White Lies" is a similar if not identical concept.
Eric sends a text message to Marie's cell phone to call him back urgently, while he is in the restaurant with the blonde actress. Marie's cell phone beeps when receiving this text message, but when Marie opens the text message, the cell phone's display shows that it is set on mute ("silencieux").