Having apparently punched and head-butted Royals defender Ivar Ingimarsson, Windass fell to the ground following a retaliatory push from the Icelandic international. Yet somehow the linesman saw just the push and theatrical fall so instructed the referee to dismiss Ingimarsson for violent conduct.
Ten-man Reading consequently blew a golden chance to take a lead in the play-off race, their 2-1 defeat condemned them to ninth place.
After the game Coppell was left fuming when Windass admitted that he conned referee Keith Hill into giving Ingimarsson the red card.
The angry Royals boss exclaimed: "I spoke to their player (Windass) after the game and he said 'I conned the referee, I conned him.'
"He made physical contact with Ivar. Ivar told me there was a headbutt and a punch, then he pushed him but the linesman saw only the last part. The referee interpreted it as violent conduct.
"If someone butts you you've got the right to push them away."
The defeat was all the more frustrating given that all of Reading's main play-off rivals bar Ipswich dropped points.
The Tractor Boys won 3-1 at Rotherham, but West Ham managed only to draw at home to Derby whilst Millwall were surprisingly thumped 4-0 at Coventry. Wigan and Sheffield United, who both played on Friday, were also defeated.
Had Reading managed to escape from Valley Parade with all three points they would now be sitting fourth with a clear lead over the rest of the play-off chasing pack. But Coppell's side must battle and scrap for their lives in the final five games of the season if they are to achieve a top six finish.
Performances like yesterday's one at Bradford continue to annoy Coppell who thought his side had finally hit a consistent patch.
The Royals boss summed up yesterday's match saying: "It was a massive, massive frustration after last week's game which was high tempo and passionate. This was completely different."
With league leaders Norwich visiting the Madejski Stadium on Monday, Reading will have to get things sorted and quickly if they are to put things back in order immediately.