We don’t support soft deletes for C&S documents due to the complicated nature of restoring meetings. This is something always on our plate to look at in the future, but it is not something that is likely to change.
Once you delete the meeting, you cannot recover it. If you don’t want to attend the meeting, please declinel/cancel it so it will be removed out of your Calendar, but the Calendar invite still places on your list view (like Grouped Entries for example)