iCloud emails disappeared from folder

Hello Lnming,

Thanks for posting in the Apple Support Communities.

Have you checked if you have an Archived folder set for iCloud Mail to store deleted emails? If you're unsure, let's be sure to check for an Archived folder and Trash folder to see if those emails may have been moved there. For assistance with checking where your deleted messages are currently stored, take a look at the following steps: Delete email in Mail on iCloud.com - Apple Support

Change the location of deleted messages

By default, messages in iCloud Mail are moved to the Trash when you delete them. You can change the folder they’re moved to.

1. In Mail on iCloud.com, click at the top of the Mailboxes list, then choose Preferences.

2. In the General tab, select “Move deleted messages to,” choose a folder or click to create a new folder, then click Done.

Let us know if that helps to locate any emails, and confirm which devices you've used to check for the folder.

Have a great day!