But they have recorded back-to-back wins and a victory over Gold Coast in Townsville next week in the final round will ensure they finish in the top four.
With Sam Kasiano missing due to suspension, David Klemmer tore into the Cowboys' pack all night, but the Dogs' attack again lacked penetration.
After back-to-back losses, fifth-placed Canterbury need to beat South Sydney next week and hope other results go their way if they are to re-enter the top four.
The visitors looked slick with hooker Jake Granville returning from two weeks out with a hand injury.
They led 6-4 at the break and kept the home side at arm's length for much of the second half. Coen Hess also scored for the visitors in the second 40 minutes.
Tries for Curtis Rona and Greg Eastwood after the break were simply not enough for the Dogs.
Eastwood had Bulldogs fans on their feet early when he scored an intercept try from a loose Michael Morgan pass in the 10th minute.
That came after Thurston opened the scoring with a fifth-minute penalty goal.
The Cowboys' first try came when Lowe burst through an Eastwood tackle close to the line.
The Bulldogs' loss before a disappointing crowd of 10,144 means Canterbury have won one of four since returning last season to Belmore. Dogs coach Des Hasler was philosophical about the loss.
"We did some real admirable things, we defended well, but you don't always want to be admirable," he said.
"We need to turn that around.
"We came up with key unforced errors in key positions on the field, and gave them the chance to build momentum and repeat-set options.
"In the second half, we made some one-on-one misses. I thought we had a dig, though. I thought the effort was there."
Hasler lamented the Dogs' top-four destiny was now out of their hands.
"Underneath, there lies the potential to turn it around," he said.
"There is enough experience and ability in this team to do that.
"The players are disappointed and frustrated because a lot of it is self-inflicted through basic fundamental errors."
Coach Paul Green was quick to point out the Cowboys were not assured of a top-four spot.
"We are not there yet," he said.
"I thought it was one of our tougher wins of the year particularly with everything that was on the line.
"We knew they would come out firing, being back at Belmore, and we were glad we matched that.
"We showed good patience, and we lacked that in those losses. We had the right mindset tonight."
The Cowboys' win means Canberra are assured of a top-four berth.
