However, I also had an issue when I tried it. Hopefully this will clear things up for you.
It seems you copied the solution and pasted it into your excel sheet. This contains spaces. Thus you are not finding for "Ball" - you are finding "Ball " (note the space at the end). As this is not what you need Excel ignores the value. To ensure you are looking just for Ball anywhere in the cell, try this:
This way "I have a Ball" , "Balloon" , "FireBall" , and " The Ballroom was big" will all be counted. Dont forget this is NOT case sensitice, so "Handball" will also be counted.
Please let us know how you get on.
I really appreciate thank you messages as a payment for solving issues :o)