Find my phone email. Notices
As far as I know Find My iPhone has always been sending out e-mails as confirmation to the user with the linked Apple ID that their device has been found. At least, I've always received confirmation by e-mail after using it.

If this was not the case for you or propably more users with the same question: 
-it has been changed to send e-mails more frequently after the iCloud-hack which was like a month ago.