Missing friend

A friend of mine went missing over a year ago. Her friends or family haven’t heard a thing from her. A police report was made the next day and. They talked to everyone they could think of, but nothing. One of my friends called the police station today and they said the case was closed. I don’t understand how because friends or family still hasn’t heard or seen from her. What could be the reason for this. Was she possibly found but doesn’t want to talk to us maybe? We’re in Michigan by the way