Did this happen to you? At a public Wi-Fi the IP address will be that of the free provider however the MAC address of the computer used will be unique. If all that occurred is that someone erased your phone, as serious as this is to you, it is a minor crime as far as the police is concerned. The odds of a police detective spending time to investigate this is next to zero and Apple will certainly not do it. If you are really serious about finding out, your best bet might be to hire a cyber crime private detective at your own cost... Your first priority should be to change your Password to a very strong one, multiple upper and lower case letters and numbers that only mean something to you. You can try restoring a backup to your phone to recover your settings and data if your device has not been locked. If it has, visit an Apple store and bring proof of purchase.