The Morocco international was handed his marching orders after receiving a second yellow card during QPR's 1-0 win over Spurs on Saturday.
"The funniest thing was at the end of the game Shaun Derry didn't even realise we were down to 10 men," Onuoha told the Daily Star.
"I don't know whether that says he was a bit spaced out or that it was just the same as usual for us because we always have to work so hard.
"There was just a real look of shock on his face when someone said that Adel got sent off. To think that is remarkable really, isn't it? I think it was Anton Ferdinand who told him. I just thought, 'Wow. I don't know what planet he's been living on to think it was 11 versus 11!'"
The West London side are three points above the relegation zone with as many games left to play.