Recover deleted calendar entries that I initiated

For the past six months, I have had a recurring set of calendar invites that I sent to someone for meetings every two weeks.  Occasionally we have had to cancel these meetings, so I deleted the ones that we did not hold.  Today, while trying to amend the invitation to make it monthly rather than bi-weekly, I someone deleted the past invitations.  This is an issue, since I need to know on what dates those meetings were held in the past.  How can I at least see which past meetings I deleted today?  Thank you.