This fact, that no one in his major remembers him, is such an outlier that the media should have been highly curious. I find it amazing that they were not.
enter
israelis don’t remember obama at columbia
for direct view via google
Again, it is not at all implausible. I went through Arizona State for four years and except for one girl friend, a family friend who knew me before, I can assure you that not one student would recognize me. And I was in a frat-—but didn’t drink, so I was excluded automatically. I lived at home after that, and didn’t spend time on campus. It’s entirely possible, but, as I showed in the link, he had a rooomate who did remember him.
"Recollections of Obama's Ex-Roommate" http://cityroom.blogs.nytimes.com/2009/01/20/recollections-of-obamas-ex-roommate/?_r=0
Another woman remembers him here: http://www.factcheck.org/2010/02/factcheck-mailbag-week-of-feb-16-feb-22/
Michael Baron, here: http://www.snopes.com/politics/obama/columbiathesis.asp
Sohale Siddiqui here: http://usatoday30.usatoday.com/news/politics/2008-05-15-3144401415_x.htm
Plus an article he wrote in the Columbia magazine, here: http://www.politico.com/static/PPM116_obamaessay.html
Graduation list here: https://rcradioblog.wordpress.com/2012/08/14/more-proof-barack-obama-graduated-from-columbia-university-in-1983/
Even Brietbart disputes the "no-Columbia" notion here: http://www.breitbart.com/big-government/2012/05/18/the-vetting-exclusive-first-obama-columbia-record-released/
Another four or five students remember him here, plus profs: http://www.thefogbow.com/special-reports/people-remember-president-obama/friends-2/
All in all, this is far more than you could find about me in four years at Arizona State U.
See the list above. Maybe a dozen or so remember him.