Why do neither of these two queries return results?
select page_id from page where username="coorslight"
select username from page where page_id=8310601338
If I go point my browser at http://www.facebook.com/coorslight I see their page. I found their page_id (8310601338) by liking them and then querying my likes.
Both of those queries work fine for me in the Graph API Explorer- check you're not forgetting to use an access token for a user who can actually see the page - the page is from an alcohol brand so is probably restricted to users >21 in the US, users >18 in the UK, etc. You must use an access token from a user that meets the restrictions in order to see the page.