Can I turn Find My iPhone on from another device?
Photo Credit: Courtesy of 3DStockPhoto (My Turn image)
If you can't find your device, turn on Lost Mode right away using Find My iPhone on iCloud.com. If you have Family Sharing set up, you can turn on Lost Mode for family members' devices, too. For more information, see the Apple Support article If your iPhone, iPad, or iPod touch is lost or stolen.