When you create an event and add an participant there is the option to not send an invitation to the particpant. Thus the person doesn't know you created an event with that person.
Steps to reproduce:
1. Create an event.
2. Add an participant.
3. Switch "send invitation" off.
No message for the participant. No entry in the calendar.
Why is that even possible? there is no reason to have a meeting without the person with that you're having the meeting knowing there is a meeting. If there is no email sent at least the event should show up in the participant's calendar or something else.