The number lives on a card you will not have on you
The chip is implanted once and then the number goes on a card, into an email, or onto a form at a clinic you changed years ago. The day it matters, someone is asking for it over the phone and you are looking through a drawer.
FichaPet puts it on the pet profile, with the breed, the sex, the birth date and the weight. Nothing about it is clever. It is just written down in the place you already open every day.