Why can"t the FBI recover the MySpace logs for the death of a teen?

Why couldn't the FBI recover the complete text of the MySpace posts that
were the cause of the young girl's death when a parent of a neighborhood
girl posed as a viscious boyfriend?

It's incomprehensible to me; would someone in the profession shed light on
why the FBI couldn't recover the MySpace files sufficient to prosecute?

REFERENCES:
http://www.bloggernews.net/111653
http://tech.yahoo.com/blogs/null/59034
http://www.foxnews.com/story/0,2933,312018,00.html
http://blogs.orlandosentinel.com/features_popculture_blog/20 07/11/girl-commits-su.html