Most items in your system (e.g., price levels, discount codes, events) allow de-activation rather than deletion.
De-activation is like a "soft delete", so you can easily recover those items if needed.
To restore a de-activated item:
Navigate to its list view
Above the "Active" column, toggle the filter to "False" to reveal the inactive items
Edit the inactive item
Set "Active" to "True"
Save + Done

To restore a de-activated event
While the method above will work for all items (including events in the Events List), sometimes it's handy to see inactive events on your calendar before restoring them.
To temporarily view inactivate events on your calendar:
Navigate to Admin->System Configuration->Calendar: Admin
Set "Show Inactive Events" to "True"
Save + Done
Now you'll see your inactivate events on your calendar, and you can restore them as needed.
When you're done restoring events, keep your calendar clean by setting "Show Inactive Events" to back to "False"
