Missing from Search

The key to getting indexed on Google is unique and compelling content for Google Search to index for people to search for and find. Google Search only indexes text. It's not necessarily the number of words that are at issue, but fewer words mean there's less chance of your site offering something unique and compelling for Google Search to index. Google Search only indexes textual content for other people to find. If there is hardly any text, therefore, Google Search may not even bother indexing the site as there's nothing for people to search for.

This is not specifically a Google Sites issue and the best advice is to read all the resources on:
Why is my page missing from Google Search?
Webmaster Guidelines
Avoid the following techniques:

Hopefully that will help you improve your Site's likelihood to get indexed.

(credit to Steegle from whom the above was plagiarised)