When you send a meeting invitation you will see it in your “Sent” folder.
If you make subsequent updates to the invitation, you do NOT see them as separate notes in the sent folder, however if you find the original note you will see that it is updated with your latest changes.
The Gory Details:
This is because the original sent message, your calendar entry and the update you just made are all one and the same document. When you open your sent message you will see it’s exactly the same document as if you opened the meeting from the calendar view.
There is no obvious way to “confirm” that the update has been sent except that, if you did not encounter any issues when you saved the update and if your calendar entry reflects the update, then it has been sent.