Mourinho told a news conference after the match that he wanted to bring Heinz to the dressing room to celebrate with the players, but the boy had left the stadium immediately after the match because he was going to do a school test the next day.
"I used a flashlight all the way home in the car to review math classes. His school agreed to postpone the test until Thursday in honor of his efforts," the boy said.
Heinze raced back to the pitch after it came off, hurling the ball to Sergey Aurier to make a lob-shot to the right-wing Brazilian Lucas Mora, who in turn passed the ball to striker Harry Kane to score 2-2.
Tottenham Hotspur striker Callum Heinz said it was the happiest moment of his life to help his team draw and then win the Champions League against Olympiakos and hugged coach Jose Mourinho.
The goal came at the start of the second half and was pivotal at the heart of the table with a 4-2 win at Tottenham and ensuring a place in the Champions League.
Images of Mourinho hugging and shaking hands with Heinz spread around the world on Tuesday.
"Things are a bit strange. I was doing my job and still can't believe what happened," Heinz, who is in his sixth season at the club as a boy, told Tottenham.
"I didn't even see the goal. I was busy collecting the ball that came out of the stadium and then I heard the cheers. I turned around and Harry was celebrating the goal and I looked at the replay on the screen and I saw exactly what happened."
"You can realize from my smile that I didn't believe what happened. Jose didn't have to do it. It was really nice to come to me. He gave me joy and happiness in my day and in my life.