All of my current activities have been deleted. This happened once before and I had to go to my deals, check their emails, and set up the activity again.
How can a mass activity delete happen?
It might be a filter issue. Make sure you are on "Owner" => "Everyone", then choose "All" on the left of the screen.
If not it might be caused by an automation.
To make sure review if an automation deletes activites on certain conditions
Turns out I believe it was a beginner's error. My calendar was being populated with emails, calls, tasks, etc., that did not have any information attached to them. This didn't have any purpose for me so I deleted them. I now realize these were probably linked to activities and consequently, I was deleting the activity along with the calendar notification.
Is there a way to include information on the calendar notification, not just task, email, call, etc? If not, how do I turn off the calendar notification for activities?