How to know if someone uses you for account recovery

Someone will need to invite you to become there recovery contact, see this

To become an account recovery contact, a friend or family member first has to invite you. When they send the invitation, you see a notification in the Messages app on your device. If you're part of their Family Sharing group, you're added as their recovery contact automatically. If not, you'll be asked to accept or decline this request. 

You can remove yourself as a recovery contact at any time in Settings on your device. 

So this cannot happen without you knowing about this procedure