The information was put onto Rangers' website on Friday evening by an anonymous source and was correct for much of Warnock's team selection.
"I couldn't believe this yesterday," Warnock told reporters.
"A QPR fan put on the website that Campbell has broken his foot, Helguson's playing, Mackie's making his debut, and Adel is out.
"This is supposed to be a supporter. You don't want many supporters like that. What an advantage for Blackburn. It does my head in when an alleged supporter does something like this.
"Obviously he's got a contact, but if he thinks he is helping me as a QPR fan, it is exactly the opposite. I don't understand supporters like that."
Meanwhile, Warnock was pleased with his side's performance at Loftus Road, but was disappointed with the equaliser that they conceded not long after they had gone ahead.
"I can't fault the lads," he added. "I thought they tried hard. Mainly I'm so disappointed with the goal we conceded - you have to make teams earn the right to score a goal.
"If you can't mark a man for a corner kick and let him have a free header, there is something wrong."
The R's, who are 10th in the Premier League table, entertain neighbours Chelsea next Sunday.