City never recovered from their shocking opening despite Robbie Brady's goal, eventually slipping to a 4-1 defeat which left them outside the top two with 12 games to play.
And Bruce said: "I've had better days. That start is something you see at school. How can you explain it?
"It's one of those freak things. I have never been involved in something like that and I don't think it will happen again for a long time.
"You have to erase it and say 'it happens'. Sometimes a kick up the backside doesn't do anyone any harm now and again.
"We have been rock solid for seven months. The one thing we needed after that was a response and I think you saw there was one.
"But you know it's not your day when you score to make it 3-1 with 20-odd minutes to go and they go down the other end and score again.
"Bolton have got some good players yet when I looked this morning they were four points above the relegation area. That shows you how difficult this league is."