Scheduling and managing events using Outlook.com calendar
Hi , first check your calendar in a browser using the same account: https://outlook.live.com/calendar/
Make sure your usual calendar is ticked in the list on the left.
If the appointments are missing there too, switch to Mail >> Deleted Items and look for them. If you find them, right-click >> Restore.
If they aren’t listed, select Recover items deleted from this folder at the top, then select the appointments >> Restore.
Can you see your appointments in the browser, or are they missing there as well?