Mary's Yahoo email account was hacked, and in the process, all her contacts in her address book got deleted. Is there any way to retrieve it? Leo says that Mary probably had her account hacked through her "secret" questions which can be guessed using a brute force attack. Once hacked, her account was used as a spam account. But it may be that her account wasn't hacked at all, and her email address was spoofed instead. That means they just can pose as Mary by using the "reply to" field.
Since she also lost her contacts, the chatroom says that Yahoo has a way to restore them. If that doesn't work, then there's no way to really get them back. The good news is that since Mary uses her iPad, it remembers the contacts and will fill them in as she goes. That's why it's so important to back up contacts. She can export them to a CSV file and then restore them.