How do I get back the mail that vanished from my Inbox?
I opened mail.app on my computer to check for important messages, and there were hundreds (typical). I have an address alias on iCloud for "Business," and a rule filtering them to an iCloud mailbox of that name. I have other rules set to highlight any messages from schools, governments, et cetera differently, but I noticed that the highlight was not present on some of the .edu messages when I opened this mailbox today.
I checked the rule, and I saw no reason that it wouldn't work correctly. It's an "any" rule including "from contains .edu" and more for unaccredited schools. Confirming immediate application of the rule upon closing the edit interface nothing changed. The same ones that it worked for before still showed up, and the ones that didn't still didn't.
Not long ago (months?) I discovered I could now have submailboxes, and created one for important reference information that I intend to save/archive. So that such things wouldn't be cluttering the Business mailbox. Reminded of this I figured it would be more organized to create submailboxes for each category of important message rather than using highlights.
So I created a new rule (depicted in image). Confirming application of the rule upon completion everything in my iCloud inbox and the Business mailbox simply vanished. It's not in the trash (neither in mail.app nor computer), it hasn't moved anywhere, the new "School" submailbox is still empty, but the "Important Information Saved" mailbox and the Junk box still have their contents. None of my other mail accounts seem to be affected either, just iCloud. I wasn't logged out, there was no undo option, and restarting didn't fix it.
Mac Studio, macOS 13.5