On a day that was supposed to be all about Albion's new striker Daryl Dike, it was an old one that came back to haunt them with Austin netting the game's only goal in the 89th minute.
Ismael's side had been the better team in the first half before QPR had a flurry of chances shortly after the re-start.
But the introduction of Dike helped swing the momentum back towards Ismael's side.
QPR then threw on Austin - with the game end-to-end from that point.
And the Baggies were adamant they should have had a penalty in the 87th minute when Conor Townsend was bundled over in the box.
Referee Simon Hooper, though, waved play on before Austin won it two minutes later.
“It was a good game from us - first half we played very well," Ismael said.
"We didn’t have the big, big, chance, but we had the one with Matt Phillips.
"Second half QPR came into the game, but it was to be expected.
“When Dike came on he had an impact on the game, but I think the game changer for us is the clear penalty on Townsend.
"Two minutes later we concede a goal. This is a big frustration for us, to concede again.
"We should have had a penalty and we should have won the game."
Ismael was in no doubt his side should have been given a spot-kick.
“It’s a clear penalty, 100 per cent penalty," he said.
"He comes from behind him, it’s clear.
“The game is 90 minutes plus and you wait for that moment.
“You can’t change anything. It’s a decision for the referee. What can you do? Jump on the ref? It doesn’t change anything."
Albion travelled to QPR without five centre-backs with Cedric Kipre suspended, Semi Ajayi at the African Cup of Nations, Kyle Bartley and Kean Bryan injured and Dara O'Shea having only just returned to training following ankle surgery.
They were also without suspended duo Sam Johnstone and Alex Mowatt.
And Ismael vowed results will improve when those players return.
"The performance I’m satisfied with," he continued.
"At the minute we need to understand that to compete with the top teams we need to have the best players we can get - at the minute we are having to change the line up, the positions.
"We are missing five key players today, and it shows in the long-term.
“We need to have our players, the best team I can pick, and it will look much different.
"The same with the bench, when you have the possibility to have an impact, just with Dike is not enough.
“It was the kindergarten on the bench otherwise, just the kids, 18 years old. It’s a difficult one at the minute.
"We need to manage the situation, but otherwise it’s a good game.
"The game changer is the penalty, it’s a penalty. You see the situation, and then two minutes later there’s the goal.
“It’s difficult one that we’re going through at the minute. We didn’t get the reward we wanted. There were some positives, but you need the best players you can get."