The London Irish full back missed out on selection for Ian McGeechan's original Lions party and has since seen fellow backs James Hook and Gordon D'Arcy called up ahead of him.
But the London Irish star has responded brilliantly, impressing in club colours in both the Guinness Premiership semi-final and final and taking his fine form back into the international arena.
"Delon is maturing as a player. He's taken his disappointment with the Lions very well," said former Lions skipper and now England team manager Martin Johnson.
"He's done very well for us. I enjoy watching him play and being part of the team. He's with us until he gets the call from the Lions.
"I hope for his sake he does get the call, though it will be nice if it's after next Saturday."
Armitage was joined on the scoresheet by Test debutant Matt Banahan who first wore England colours in the non-cap match against the Babaas at Twickenham nine days ago.
The Bath wing won the man-of-the-match award for a powerful and industrious all-round display at the home of Manchester United Football Club.
"It's all about taking your opportunity because you don't know whether it's your first and last time putting on an England shirt," explained Banahan.
"You've got to play with all your heart and give everything. If you're good enough you will keep playing.
"All that was going through my head was, 'This is my first game, I've got to enjoy it'. I'll never forget this day and I'm definitely pinching myself."
Brive fly-half Andy Goode added 22 points with the boot as England took a 1-0 lead in the two-match Test series against the Pumas.
England now travel to Argentina for the return match next Saturday in Salta, with skipper Steve Borthwick confident his side can it make it two successive wins over the World Cup semi-finalists.
"Now we need to review this game and look at what we need to improve on and what went well to see where we take the game to the next stage for next week," said Borthwick.
"We need to ensure that we travel well and get over there is the best state possible, so that come next weekend we're as well prepared as we can be.
"We've got a fantastic group of people - the coaching team, the management team, the conditioning and medical side and the players. People who all want to work very hard to help England do well. When you've got that, you've got to work hard, be precise and learn from your mistakes to go forward."