When Lee Nicholls guessed right to deny Daryl Murphy from the spot in the 89th minute, Dons defender Joe Walsh admitted he thought they were out of the woods.
Having played the final 24 minutes with 10 men, after George Williams' red card, Nicholls' latest penalty save kept the score at 0-0 heading into stoppage time. But Murphy would get the last laugh as he swept home the winner, breaking Dons' hearts.
"We had three minutes left and thought we'd done it," said Walsh. "It was a sucker-punch really but that's football – you cannot switch off for one moment.
"Everyone is gutted. After Lee made the penalty save, everyone is gutted. There is no point getting down about it, but we have to go again on Monday, and start picking up results like we know we can.
"The performance was so much better than is has been. We played so much more football which we know we can do. We played so well, but got killed in the 92nd minute. We're looking much better so we're looking forward to the next game.
"Luck isn't going our way at the moment, with Jordan (Moore-Taylor) going off and George getting sent off. But we have to stick together and go again next week.
"George is gutted, as soon as we came in he apologised. People make mistakes, he knows it was a mistake, we have to get on with it."