I found this image which i think will be helpful when thinking of a slogan:
But instead of the word 'visible' link it with sound, so something like heard or understood. As i can't use the same slogan.
MAKE THE HIDDEN HEARD- which i think would work really well as it links with the person being hidden because they don't have a voice, therefore they can't be heard.
Also hidden because the QR code hides it until it is scanned.
I don't know wether i will be able to get away with this because it's a bit to close to Nike's slogan, so i will think about other possible slogans.