An iPhone can be marked as lost on Find My App, but this will not automatically report the theft to the police. In order to officially report a theft, you need to notify local authorities. The police will ask for information about the lost iPhone including its IMEI number. You can ask your phone provider to get this number if you aren’t sure. Keep a record of the crime reference number once the report is filed, since this number will be needed if you make a claim with your insurance.