The Owls rued two penalty incidents as they were held to a 1-1 draw by QPR at Hillsborough on Tuesday.
First, Atdhe Nuhiu missed from 12 yards before the visitors broke on a rare counter attack and scored through Daniel Tozser.
Then, a minute from time, Kieran Lee went down in the box but the referee waived away the home side’s appeals for a second spot-kick.
Carlos Carvalhal said: “I do not like to talk about the referees as you know but tonight I think that was a certain penalty.
“I have seen the images and I have spoken to Kieran Lee, who would tell me if it wasn’t a penalty, but he said it definitely was and I believe him 300%.
“I don’t like to focus on this decision though because we should have taken our chances and we have to take our part in that.
“We created some good opportunities but we did not take them, but this is what happens in football.”