Thornber said: "We defended it and didn't look like conceding, and then they've scored with the only threat they had.
"You've got to kill teams off and you know what's coming if you don't put the ball in the back of the net.
"We had some good chances, and Nicky Law should have scored in the second half.
"I thought we absolutely dominated the game and we created enough chances to win three or four games. That's probably our best away performance of the season."