Former Nottingham Forest winger Burke came off the bench in the second half of a gritty game, whipping in a cross in the 89th minute to set up Leipzig's dramatic winning goal.
"I didn't realise what was going on today," the forward told the Daily Mail after the game.
"I only found out just before the game that I was on the bench, but wow! It was a great to win, particularly against a team like Dortmund.
"I just knew I had to get the ball in the box, and then anything could happen."