I was testing the connection with the remote calendar server, and I tapped on the menu bar on CalDAV and selected "Refresh calendar list".
After refreshing, the app displayed TWO instances of the same active calendar that I was using.
I long-tapped on a duplicate calendar and selected "Delete collection".
Both duplicates on the app, and the ENTIRE (important and active) calendar on the server - got deleted!
And I have no backup data!
This option should come with a warning that says something like:
"WARNING! YOUR ENTIRE CALENDAR SITTING IN YOUR REMOTE SERVER WILL ALSO BE DELETED! DO YOU WANT TO PROCEED?"