The message iPhone unavailable is considered a security message, and it appears when there have been numerous wrong entries of passcodes on the iPhone. This message signifies that the phone has been locked so as to protect the content in it. The iPhone may display a timer or may require the device to be erased depending on the number of wrong entries. When you receive this message, it is not advisable to input random passcodes since this will cause a more stringent lockout. Before you choose to erase your iPhone, it is recommended that you ensure all the important data you have on the phone is backed up somewhere else, preferably in the iCloud. When you are handling missing data, you can consider using Datarecovee for supported iPhone data recovery information.