With LINE, chat rooms are automatically created for recently added friends. "Start chatting with your new friend now!" is always the first message in these chats.
Also, if you or your friend turn the "Allow others to add me" setting ON, your chat room may be recreated and appear at the top of your chat list.
If a chat with a friend you haven't messaged recently appears at the top of your chats, it may be because that friend turned their "Allow others to add me" setting ON.
Rest assured that this message does not mean an account is being impersonated or has been stolen.