Lost device

Don'ts

If you remove the device from your account after you erase it, Activation Lock will be turned off. This allows another person to turn on and use your device.

Do's

• Mark As Lost.
• Erase your device.
• Apple Care+ :- file a claim for your lost or stolen iPhone. (If you had Find My enabled)

Did you enable Find My?

If you didn't turn on Find My [device] before your device was lost or stolen, it can't be used to locate your device nor you can use the IMEI number for tracking the device.

The best action would be to Change your Apple ID password and change the passwords for other internet accounts on your device. This can include email accounts, Facebook, or Twitter, etc...

If you had "send last location" enabled, the device will display the last location for 24 hours. It's likely that your battery died, the device is not on a network, or the device did not have FindMy enabled if you couldn't find it online.

If you have Apple Care+ with theft and loss, you can file a claim. Otherwise, you'll need to purchase a new device.