With Sami Khedira hurting his ankle in the warm-up, Kramer, 23, was brought in for his first competitive start at international level.
But Kramer lasted just 32 minutes at the Maracana on Sunday, sustaining a head injury and was substituted.
He could remember little as he celebrated with his team-mates, but was more focused on trying to wish his grandmother a happy birthday.
"I can't remember very much but it doesn't matter now," Kramer said.
"I have to send regards to my grandmother. She has a birthday today and I couldn't reach her."
Germany defender Jerome Boateng never doubted his team as he saw a tiring Argentina before Mario Gotze's 113th-minute winner.
"Argentina defended well, but tired in extra-time, and we had more energy," he said.
"I've always believed in the victory."
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