Yes, it was an unexpected and good job by the defense to stop the Bears there. That was completely unknown, as you say. The odds aren't exactly in favor of the Bills defense.
Edit: Thanks for repeatedly implying I am a loser. As a fan of the worst team in the NFL (as I assume are you) being called a loser is nothing new. Thanks for your comradery as a Bills fan.
As far as being disappointed, I suggest to you that having the ball on the Bears side of the field was their best chance to win the game with under 3 minutes to go. Of course the game didn't end when that drive fizzled there, but expecting the defense to hold and the offense to drive a long field with less than a minute is counting on a miracle. It didn't happen and it doesn't happen often. For the 2010 Bills, it has yet to happen. That's all I meant by the original comment.