Just a general answer....existence check "Overridden" means that the check initially failed during data entry, but was manually overridden when an analyst reviewed the file and either found proof or requested proof and received it from the attorney.
Also, overheard a conversation where a beneficiary/alien wrote in and requested his file information under the Freedom of Information Act.
While creative, this approach has a couple of flaws. First, it's unclear whether a foreign national even has status to make such a request....even if they do, the application is considered by the Feds (surprise) to be the property of the Employer, not the beneficiary. That is why telephone calls, e-mails, faxes, letters, personal visits all get the same response...."go ask your employer or the agent/attorney to inquire".