The Australian then skipped the post-match function, instead heading back to the team hotel and having a few quiet drinks with friends.
Nine years on and now caretaker coach of Scotland, Johnson might allow himself a more exuberant celebration if he can end his time in charge of the national side with an odds-defying victory in the same ground.
Since he took over from Andy Robinson, and during the time spent waiting for Vern Cotter to take over the head coach's job, Johnson has stressed that his team are on a journey of development, but thus far all we have seen have been baby steps.
If Scotland can win here in Cardiff, this afternoon in the final game of their RBS 6 Nations campaign, the achievement would be a massive stride forward. "It would be a shot in the arm - a great shot in the arm," smiled Johnson "They say winning is contagious. You learn from experiences like this and you can't replicate them, try as you might.
"This [the Millennium Stadium] is a cauldron like nothing else in the world. If we can win here, it would be a pretty good injection of confidence, that is sure."
The towering stadium may indeed be a cauldron, and arguably the most atmospheric venue in world rugby, but there has been a curiously muted feeling around the Welsh capital these past couple of days. A year ago, the city was in a tumult of anticipation of a momentous championship decider between Wales and England; unsurprisingly the build-up to a game that has been billed as the battle for fourth place has been a little more subdued.
Not that Shaun Edwards, the Wales defence coach, was in any hurry to agree with a suggestion that today's match could be written off as meaningless. Edwards, the former Wigan and Great Britain rugby league player, is a competitor to his marrow and the fact there is no title at stake this year diminishes that not one bit.
"It's not a dead rubber," he hissed. "It's still an international match between Scotland and Wales. There is no such thing as a dead rubber there. We have a proud home record this year and want to go through the tournament unbeaten at home. The draw was difficult for us this year, with Ireland and England away, and we lost those two games, but we are determined to win all our home games."
Johnson and Edwards are very different characters but were following the same lyric sheet in that regard. "It is an important game," Johnson said firmly. "It is an important game to show your wares and because it is a Test match. There is no such thing as a dead rubber."
Johnson smiled as he recalled his first experience of the Millennium Stadium, as a member of the victorious Australia side's backroom team at the 1999 World Cup. His years with Wales were marked by controversy and huge swings of fortune but nothing could diminish his enthusiasm for the setting.
"I had an absolute ball in my time in Wales, good bad and ugly," Johnson said. "I can't replace any of that and wouldn't replace it. There are so many things I owe this country for that I will never forget it. Now I am on a different journey with Scotland and will feel the same when I have finished there.
"The beauty of it is the ambience [around the Millennium Stadium]. You are right in the middle of the city and it is a special thing being so close. You have to enjoy this. This is a thrill, the thrill of lifetime to play here and to coach here."
And to win here? Johnson was never going to make himself a hostage to fortune with that prediction. Wales may have dropped a couple of notches since last year, but on paper they are still a far better side than the Scots. The fact Wales have made six changes, only two of them enforced, from last weekend's loss to England suggests a degree of frustration, but Johnson is well aware of the threat they still pose.
"They will be disappointed with their results but they haven't been far off have they?" he said. "They've been to places that are hard to win at, to Twickenham and Ireland. Their form has not been as bad as people have said. The competition is tough and they are a great rugby side with a great tradition that is second to none."
In fairness, it has sometimes been difficult to square Scotland's performances with the scoreboard at the end of their games. They were probably closer to Ireland than their 28-6 loss on the championship's opening weekend suggested, but certainly further behind England than even a 20-0 drubbing declared.
And it goes on. They should have beaten Italy by more than one point. And they should have beaten France rather than cough up a silly penalty near the end and hand victory to their opponents.
"We are going to learn when we need to squeeze a team and [when to] release that pressure," Johnson said. "We do not have that balance right as a team. We spoke about that during the week. When we kicked the goal last week [to take the lead against France] there were seven minutes on the clock and we tried to play a big play.
"Sometimes you need to be a bit patient. We want to play attractive rugby and we think we possess the skill set to do it, but there are times in games where you have to say, 'okay, cut our losses and get out of town'."
If they can win in Cardiff today, Johnson, his players and a few thousand Scottish Fans will be in no hurry to do that.