Back in March 13, 2008 Gladwell claims his story is not true.

See the end of his blog post where he write:

There is a disclaimer at the end of the This American Life broadcast, to the effect that the Moth is a place where "people come to tell both true stories and occasional tall tales." As I think should be obvious if you listen to it, my story definitely belongs to the "tall tale" category. I hope you enjoy it. But please do so with a rather large grain of salt.

http://gladwell.typepad.com/gladwellcom/2008/03/tall-tales.h...