Freddie Sears, on loan from West Ham United, had appeared to give Palace the lead after 34 minutes after a quick counter-attacking move.
The youngster's celebrations were cut short as the strike was disallowed. The ball had ricocheted back out of the net and the referee Rob Shoebridge, after consulting an assistant referee, ruled their had been no goal.
Warnock argued with the officials, and continued his protest long after Nicky Maynard had scored a late winner to seal all three points for the home side.
"I feel sorry for the referee because he didn't get any help. But how can I mark him when he spoils an otherwise good display with a mistake of that importance?" he said.
"We were cheated. And I'm not saying that against the referee because he didn't mean to get it wrong. We can put a man on the moon, time serves of 100 miles per hour at Wimbledon, yet we cannot place a couple of sensors in a net to show when a goal has been scored.
"I thought Gary Johnson and his players could have shown more sportsmanship because they knew it was a goal, like everyone else. But I'm 60 years old and maybe I expect too much."
It is still early in the season, but after two fixtures Coventry City are top of the Championship table. They were 2-0 victors at Barnsley on Saturday to ensure they are the only team in the division with maximum points, but their manager Chris Coleman played down expectations.
"We've got a better feeling in the squad than last year, but we still need to improve and I'm hoping to bring one or two in."