This could have been one of the Warriors' most significant wins of the season – instead it will go down as another gut-wrenching loss.
Cowboys fullback Valentine Holmes kicked a 79th minute field goal – from nearly 40 metres – to clinch a 29-28 victory for the home side.
Of all their defeats this season, this one will be particularly hard to take, as the Warriors looked to have the game in the bank after an impressive second-half revival.
But the Cowboys managed a Houdini act, with a converted long-range try to level the scores, before the stunning snap by Holmes.
Coming ahead of the bye, the Warriors will be left to reflect on what might have been.
Seemingly down and out trailing 22-6 at halftime, the Auckland club launched a remarkable comeback.
Powered by the impact of Bunty Afoa and Ben Murdoch-Masila, they produced an almost flawless period, with four unanswered tries in the space of 22 minutes.
Ahead 28-22 with six minutes to play that should have been enough, before they were caught napping down the short side and Hamiso Tabuai-Fidow's pace did the rest.
The Warriors will rue their poor first half.
They were far too lateral, continually going sideways against a set defensive line. At times it felt they had too many playmakers, with neither of the halves taking control, while Scott Drinkwater ran the show for the home side
The Cowboys played to a no frills, efficient pattern. Their mobile forward pack punched holes through the middle, before they exploited the space in behind.
Earlier, the Warriors made an ideal start. Good vision from Wayde Egan allowed Kodi Nikorima to put Euan Aitken over in the corner.
But the Cowboys wrested the momentum back, forcing three goal-line dropouts in quick succession. The pressure eventually told, though Adam Pompey and Marcelo Montoya got their wires crossed, allowing Kyle Feldt a soft run to the line.
The Warriors had territory – but no cut through – as their attack lacked variation. A fortunate captain's challenge gifted the Cowboys possession, but the Warriors again looked misaligned on their defensive edge, allowing Murray Taulagi to dive over in the corner.
Jazz Tevaga's 30th minute sinbinning was a flashpoint, for a hit that was so late it was almost embarrassing. The shorthanded Warriors did well initially, then leaked two tries in three minutes just before halftime, with Jake Clifford chasing his own grubber, then Scott Drinkwater finding space up the middle.
It wasn't pretty, as handling errors contributed to the pressure.
Nice footwork from Walsh and a no-look pass from Tuivasa-Sheck sent Aitken over just after halftime, to get the revival going, before a moment of pure magic from Walsh, with an 85-metre run to the line.
The 18-year-old showed great awareness to back up Montoya after a Cowboys spill, lightning speed to bolt free, then strength to force the ball in a desperate last-ditch tackle.
After Tuivasa-Sheck earned a goal-line dropout with a brilliant chase the Warriors were level, with Montoya profiting from a precise Walsh cut-out ball.
Murdoch-Masila's 64th minute try, trampling over the top with Clifford off a precise Egan pass, took them ahead.
It looked like the Warriors had done enough, before Tabuai-Fidow's spectacular try.
But there was still another chance, as Chanel Harris-Tavita missed his field goal attempt from nearly in front, before Holmes nailed his.
Cowboys 29 (Kyle Feldt, Murray Taulagi, Jake Clifford, Scott Drinkwater, Hamiso Tabuai-Fidow tries; Valentine Holmes 4 cons, field goal)
Warriors 28 (Euan Aitken 2, Reece Walsh, Marcelo Montoya, Ben Murdoch-Masila tries; Kodi Nikorima 4 cons)