From my experience outlook flags emails as unimportant, that are quickly deleted, or deleted while being unread. So for me it’s not too far off.

Once you decline a meeting, it’s gone for good in your calendar. If you accidentally declined, you need to ask for another invite.

If you decline a meeting the original meeting will be moved to the trash. So go to trash and you can accept it again.

Pharao ants?

Enemy of the State and Gattaca comes to mind