What year was your alumni directory published? That's important because he could have first appeared as Columbia alum at a much later date.
His transcript, of course, would answer a lot of questions, but he refuses to have it released - if indeed it does exist.
From the 1997 Columbia U. alumni directory:
Obama, Barack Hussein, CC ‘83 BA, 1617 S. Beretania #1008, Honolulu, HI 96828