"I've never heard of anything like this in an international game," Hamren told a news conference after Sweden struck with four goals in the last 31 minutes at the Olympic Stadium.
"I can't explain it," he added with a smile and a shrug of his shoulders. "But I think I'm going to sleep well tonight."
Germany dominated the first hour and were in complete control thanks to two goals by Miroslav Klose and one apiece from Per Mertesacker and Mesut Ozil.
"No, I didn't want to go home when we went 3-0 down at half-time," said Hamren. "I wanted to see if we could show strength and pride.
"If you're a loser you want to go home but if you're a winner you stay and fight," he added after second-placed Sweden took their points haul to seven from three games thanks to goals from Zlatan Ibrahimovic, Mikael Lustig, Johan Elmander and Rasmus Elm.
Germany coach Joachim Low was also perplexed after the group leaders dropped their first point in the fourth game of the campaign.
"It was an extraordinary match," he said. "Any time you lead 4-0 and end up with a 4-4 draw the disappointment will outweigh everything else.
"Sweden were invisible for the first 60 minutes. We have to learn our lessons from this."
The German fans jeered their team after the match but Loew said his squad would bounce back.
"I don't think it'll do any lasting damage to my players," he explained.
"Their feet didn't leave the ground when we played so excellently to win 6-1 in Ireland on Friday and they won't be hanging their heads in despair after this 4-4 draw."
