The two clubs fell out over the issue and the Us are still pressing for compensation from their East Anglian rivals over the matter.
Lambert was given a hot reception by the Colchester fans at the Weston Homes Community Stadium, but Boothroyd was more concerned about the nature of his side's heavy defeat.
"There was a lot of hype, excitement and build-up before the game," he said. "There's a way to win which we've done plenty of and there's a way to lose. If you're going to lose, you have to make sure that you do all you can to make sure you lose to the better team.
"I just felt that out of the five goals, we gave them four of them. They were silly, individual errors that you don't see on a park pitch on a Sunday. We didn't take our chances when we had our dominance in the first half and if you make silly errors, this is what happens."
Source: Team Talk