Find My iPhone activated on its own

the alert of find my phone just rang on my iphone but normaly the only other device with my apple account is my ipad wich i have with me and i never went into localisation to find my phone. is it possible to know if my account was hacked? is someone connected to my apple account without me knowing?

[Re-Titled by Moderator]

Original Title: Find my phone activated on its own?