Where to Find Your Messages After a Security Update
To ensure that security updates for the Yahoo! Messenger application are correctly applied, Yahoo! Messenger may close and reopen during the update.
If you had enabled archiving through Yahoo! Messenger and have previously communicated with the person who sent you the offline message, the message should be available in your Message Archive under the name of the person who sent you the message.
If you did not have Yahoo! Messenger set to archive messages, or if you had not previously spoken with the user sending the message, you will not be able to recover the offline messages.
If you would like to read more about the latest security updates, please visit the Yahoo! Messenger Security Updates Page.