Here are a few troubleshooting ideas when a file or folder is missing in Outlook:
1. Verify Folder Location: Double-check the location of the missing folder within Outlook. Ensure you've thoroughly searched both your main mailbox and any subfolders where the folder might be located.
2. Check Deleted Items
3. Utilize Outlook Search: Use Outlook's search feature to look for the missing folder. Try searching by the folder name or using keywords related to the emails within that folder. Sometimes, the folder may not be visible due to sorting or filtering settings.
4. Searching Outlook in the web version might be best to start to ensure that it's not an issue with the desktop application. If the folder might be in a shared mailbox, you might need to open the shared mailbox on its own by clicking on the profile icon on the top-right in Outlook web and clicking on open another mailbox.