A place to start would be to see if the plan has filed within the past 3 years. You can do that directly on the Department of Labor's website. http://www.efast.dol.gov . You will need to go to the search tool for submitted forms. Currently you can search for filings from 2009 to the most recent filing. That should tell you who is responsible for the plan, and where to contact them.
Call HR at your former employer, and get the phone number of the plan administrator. The plan administrator will be able to provide you information and send you a statement. If you open a rollover IRA, you will need the statement
call the HR department of your former employer