Here is what the Baseball Almanac has to say:

"My main aim was to win. I was more tired than nervous. All I know is that we lost. What's so historic about that? Didn't anyone else ever lose a thirteen inning shutout?" - Harvey Haddix

Thirty-six consecutive batters were retired by Haddix before the thirteenth inning - when it all ended on an error, an intentional walk of Hank Aaron, then a double!
Don Hoak, who was charged with the error in the thirteenth inning, said before the game, "That was a pretty good run down (pre-game discussion). If you pitch that way, you'll have a no hitter."
After the game, Lew Burdette told the media, "I called Harvey that night in the visiting clubhouse. I told him 'I realize I got what I wanted, a win, but I'd really give it up because you pitched the greatest game that's ever been pitched in the history of baseball. It was a damned shame you had to lose.' "

You can read it at:
http://www.baseball-almanac.com/boxscore/05261959.shtml