Remember to have your I-20 on your person and not packed away in checked luggage since you go through inspection before claiming bags. That said, if you forget your I-20, you should ask the immigration official for an I-515 upon entry, which will allow your admission in F-1 status for 30 days. With an F-1 visa you are normally admitted to the U.S. For 'duration of status' (D/S,) but if you are missing the I-20 it is most likely you will be admitted for 30 days with an I-515.
International at Columbia
Visit
505 Alfred Lerner Hall
2920 Broadway
New York, NY 10027
Call: 212-854-0720
Fax: 212-854-6972
Office Hours
Monday–Friday
9:00 a.m. to 5:00 p.m.