But the Millers defender spectacularly headed into his own net two minutes from time to put the play-off chasing Wearsiders on terms with their first effort on target - with a Rotherham player scoring at both ends for the second successive game.
Despite the shattering development, the Millers remain favourites for a top-two finish ahead of third-placed MK Dons and are a point in front of them with one game to go. MK visit Plymouth, who occupy the final play-off spot, on Saturday, while Rotherham head to Gillingham, who are fighting for their lives at the foot of the table.
But for the next 24 hours, Rotherham's players are likely to be low as they lick their wounds, before attention switches to the trip to the Priestfield Stadium.
Warne, whose side were relegated in the 88th minute at the end of last season at Cardiff, said: "It was a good game. But when you are 1-0, you are always vulnerable and obviously, Sunderland have thrown the kitchen sink at it, rightfully so.
"I thought we'd rode the pressure quite well. But we just needed that second goal which we didn't get and you are always susceptible for one ball or cross or clearance.
"Unfortunately, it wasn't meant to be. But I said to the lads I was really proud of them and love them - they are amazing kids. They are absolutely devastated.
"I am a fatalist. If it isn't meant to be, it isn't meant to be - you just go onto the next game.
"To come here and win would have been something that would have stuck with us forever. I said that the date - the 26th of the 4th would have been something that would have connected us forever.
"It would have been some feat for us as a football club to get promotion to the Championship in the hardest League One I have ever seen - and to come away here and win.
"It is sore...They feel down. I don't know if it makes it worse, but we found out that Wigan (leaders) lost as well. It was like: 'Oh, my God..'
"But life is never fair is it..I said to the lads that no-one has died and you see everything that is going on in the world lately. You just conceded a goal late on. We haven't been relegated and even if we don't win at the weekend and don't go up, we go into the play-offs.
"The fact that is (football) is such a rollercoaster and is so unpredictable is why everyone loves it."