Here's a description of the 2002 game:
http://www.team237.com/2002game.html
Here's a good photo of their robot that year:
http://www.chiefdelphi.com/media/photos/12168
Their feet were made from filecards. They didn't actually lift the cards, instead they shuffled them back and fourth to move the bot forward. Try it yourself, put a filecard face down on the carpet and try to push it back and fourth. Now imagine a hundred pounds of weight on the card and you can see why nobody could push 71 backwards.
Once 71 had the goals that year could be pushed sideways, but not backwards. You can see it happen in one of the videos I have from 2002, but I don't remeber which one.
http://www.students.ccsu.edu/~rodriguezjel/2002/