See deleted events in your trash (computer only)
When you delete an event you created or have edit access to, it stays in that calendar's trash for 30 days. When you go to the trash, you can restore events, or delete them forever.
Note: Anyone who has "Make changes to events" or "Make changes AND manage sharing" permission for the calendar can see and move events in the trash.
On your computer, open Google Calendar.
In the top right, click Settings Settings and then Trash. You'll see the events that were deleted from this calendar.
To delete an individual event, next to the event, click Delete forever Trash.
To delete all selected events, above the list, click Delete forever all selected Trash.
To restore an individual event, next to the event, click Restore Undo.
To restore all selected events, above the list, click Restore all selected Undo.
To delete all events, click Empty trash and then Empty.
I got the above from here... [Link: support.google.com]
And the little search Iíve done. Comes up with people complaining about this issue since December 2018.