What's Missing?

I heard the following on a CD I own by Jack Canfield.  You may recognize the name as the author for the "Chicken Soup For The Soul" book series and from the book/DVD, "The Secret".

He simply said the following:

"1, 2, 4, 5, 7, 8, 10

What number are missing?"

The answer will astound you but I'd really like for YOU to tell me what you think so please reply!  I will post the answer tomorrow.