All calendar entries lost across iPhone 4, iPad, MacBook Air after iPhone upgraded to iOS 7. Help?
You might want to put both devices in offline mode (or power down the router) in case the duplicates were not really and the calendars were deleted.

You can use another computer (or a web browser) to log into iCloud.com and inspect the calendars as far as Apple sees things.

If the calendar data is still in the cloud, then your missing data is due to an error on each device or a temporary network condition.