The Whites went down to Frazier Campbell's second-half effort and Warnock accused referee Mike Dean of being in a bad position when Cardiff captain Mark Hudson appeared to handle the ball.
"It is a cruel game sometimes. Everything about this match was cruel," he said.
"We missed open goals and the young lad (Byram) made a schoolboy error. I thought Mike Dean was brilliant but he didn't see the handball, when we all appealed, because he was in a bad position and should have been in a better one.
"He had three or four bodies in the way. The linesman could have helped him out, but they don't, do they. Then there was another handball in the 93rd minute that wasn't given.
"Our two centre-halves were magnificent, we played some good stuff against the top-of-the-table team and were better than them, so it's very frustrating that we got nothing."
- Sports & Recreation