I had a storm lay my corn almost flat one time (or 2). If you Leave it Alone there is a very good chance it will straighten back up and continue to grow, almost as if nothing had happened. But if you try to be a good gardener and "help" it out, you may lose it. I know it sounds strange, but that is my experience with it.
Also, I do not remember how long it took for the corn to straighten--sorry
Good Luck & let us know how it turns out!!!