McCormack came closest to breaking the deadlock at Fratton Park when his exquisite chip from the left corner of the area after 54 minutes struck the underside of the bar.
The ball appeared to bounce over the line and Robert Snodgrass followed up to head the ball home, but his effort was ruled out for offside.
Having watched the incident back after the final whistle, Warnock was convinced McCormack's effort crossed the line.
He said: "McCormack's shot was a metre over the line. It's embarrassing really when you see it. It's not even close.
"Apparently the television pictures here are not so good, but if they want to borrow ours, they'll see it's not even close.
"I've asked the official and he said he was in line about 12 yards away. He obviously didn't see it.
"But in fairness, there was a certain handball against us in the first half and that was the same linesman. The sun was obviously causing a problem out there."
Portsmouth were denied a penalty in first-half stoppage time when Darren O'Dea appeared to handle in the Leeds area.
The resulting penalty would have given Pompey an opportunity to claim three points, which would have lifted their Championship survival hopes.
Instead the draw left them second from bottom following their 10-point deduction for entering administration and boss Michael Appleton was keen to forget his side's latest slice of misfortune.
He said: "I felt that it looked like a blatant penalty and having watched it back, it has told me what I thought at the time.
"But that's the way it is at the minute and we have to move on quickly."
Appleton's side were well backed by a partisan 17,571 crowd at Fratton Park and the manager admitted he was delighted with the unity in the Pompey camp.
The squad agreed to defer their January wage packets to help keep the club afloat, and Appleton said the move has brought the players closer together on the pitch.
He said: "The players are pretty much galvanised together and the unity they've got comes from making decisions like they've had to make with the wages.
"To be quite frank, if they didn't do what they did, where would the club be? Would we have a club?
"Everyone wants the same two or three things. Firstly, we want to try and stay in the Championship, and we've got 14 games to do something about it.
"Secondly, we want to find an owner who wants to take the club forward, stabilise it for a number of years and not use it as a stepping stone or somewhere to hog the limelight for a year or two."