Take a look in the MODx database to see if the content is still there.
The modx_site_content table holds the page contents.
You can use a database browser to look (the PhpED editor has a very nice one built in) or you can use PhpMyAdmin. In PhpMyAdmin, click on the browse icon next to the modx_site_content table. Then click on the edit icon for the page you had trouble with. Look at the "content" field. It should contain all the content for that page.
If it’s not all there, the database has been corrupted or hacked. If you have an sql backup of the database, you should be able to restore it by importing that file. (You do have a backup right?

)
Bob