Hannes Halldorsson (Getty)
Halldorsson was the hero when he palmed away Messi's spot kick in the 63rd minute, correctly gambling that the Barcelona talisman would shoot to his right.
The man-of-the-match described the moment, which kept the score level at 1-1, as "a dream come true" but also said it was the result of painstaking research into the five-time world player of the year.
"I did some homework because I knew this was a situation that could come up. It was a long shot but it happened," he said after the tie at Moscow's Spartak Stadium.
"I looked at a lot of penalties from Messi and I also looked at how I've been behaving during the last couple of penalties.
"I tried to get in their minds, so they'd be thinking about me. I had a good feeling he'd go this way today."
He said the draw felt like a win for Iceland, who are making their first World Cup appearance but famously eliminated England at Euro 2016 to reach the quarter-finals.
Halldorsson said the Argentina result was similar to Iceland's draw with Cristiano Ronaldo's Portugal at those championships because it provided a springboard to make it to the knockout phase.
"We were playing against one of the best teams in the world who had the best player in the world," he said.
"It's especially important for us because it helped us get a point, which is important for us to reach our goal to get out of the group."
Iceland's next opponents are Nigeria in Volgograd next Friday.