The Reds led 24-3 midway through the second half on Sunday, but in a replay of last season's Suncorp Stadium clash, had to withstand a late Drua flurry and somehow hung on.
"Tell me about it," Reds coach Thorn winced.
"Really frustrating; we were determined to drag them back in with our errors and sloppiness.
"What's that saying? 'Snatch defeat from the jaws of victory?' We're specialists at that."
"For us, it's just not good rugby. It's a win, but it doesn't feel like that."
Josh Flook should have had a first-half hat-trick, dropping a brilliant short kick from James O'Connor as the line beckoned after already crossing twice.
And Taj Annan was slick in his starting debut at No.12, setting up two tries in the second half and defending well in place of concussed Wallabies centre Hunter Paisami.
Those slick moments were few and far between in a sloppy Sunday afternoon performance that featured 32 penalties blown by referee Reuben Keane.
Summing things up, Harry Wilson misunderstood a call from long-time friend and teammate Fraser McReight, flinging a pass straight into his face.
Still, the hosts seemed to be cruising when Annan's cut-out pass put Suliasi Vulivanu over for a 21-point lead.
Leone Rotuisolia inched over to give the Drua hope and, relishing the steamy conditions and open spaces, cheered home Kalaveti Ravouvou and Iosefo Masi tries.
They looked destined to roll through the Reds again for a match-winner, before try-scorer Harry Wilson dragged down a defender and winger Filipo Daugunu was the unlikely man to steal possession with a game-winning pilfer.
The Drua were coming off an emotional home victory over defending champions the Crusaders.
"I'm a little bit disappointed ... (in the second half) we got down to work, got back into the game," coach Mick Byrne said.
"It would have been nice to be like that for 80 minutes ... we know we're 80-minute players, we know we can play that."
The result leaves both teams at 2-2, with the Reds' next task in Melbourne against the improved Rebels.
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