Austin thought he had given the hosts the lead at Loftus Road on Saturday when he slotted home after Manchester City goalkeeper Joe Hart knocked a free-kick into his path.
However, referee Mike Dean ordered the kick to be retaken, as television replays showed that Hart had in fact kicked the ball twice.
With the rules stating that Hart's free-kick had to clear his area before being touched by another player, Dean's decision was ultimately correct - although Redknapp admitted he was initially unsure of what had happened.
"No one seemed to realise what it was for," he said at his post-match press conference. "Obviously he [Hart] has had two touches.
"I didn't realise he'd had two touches of the ball when he kicked it, I just thought he kicked to Charlie, but he's obviously had two touches.
"If the rules say you can't touch it twice there's nothing you can do about it. I just asked the fourth official and he said 'He's touched it twice, and the rule is if he does that it's a retake'."
Discussing the result itself, Redknapp was left with a sense of what might have been, as QPR were twice hauled back by Sergio Aguero after Austin and a Martin Demichelis own goal had given them the advantage.
"I'm disappointed, I thought we worked hard enough and played well enough to have won," Redknapp added.
"I thought they were on the ropes. They came back and got the equaliser out of nothing, and I felt when we went 2-1 up we would go on and win."
