If you store an email in a custom folder, and then reply to this email, Outlook may not store a copy of the message in the Sent Items (unless you change the settings). If a search does not reveal where the email appears, follow the steps below to see if it prevents the issue from recurring:
Outlook 2010
- Click the File tab and click on Options (under Help).  Â
- Click Mail in the left pane.
- In the Save Messages section, look for "When Replying To A Message That Is Not In the Inbox, Save The Reply In The Same Folder"
- Ensure the box is NOT ticked
- Click OK
Outlook 2007 / 2003
- Click Tools
- Click Options
- Click Preferences (Tab)
- Click E-mail Options (button)
- Click Advanced E-mail Options (button)
- Under "Save messages", look for "In folders other than the Inbox, save replies with the original message".
- Ensure that the box beside it is NOT ticked
- Click the OK button three times
For more information on why Outlook has this setting, please refer to this article.
