Is Obama's Columbia Existence Fabricated?

SEE HERE It seems very strange that Obama's existence at Columbia is so ephemeral. Did he really go to Columbia or is his presence there a fabrication. A few years back someone claimed that he worked for the CIA and the Columbia story was part of his cover. Could that be true? I don't know, but I find it hard to believe that out of a major numbering 150 students that no-one would remember him.