Man, he definitely noticed the bruise. That's not the thing that you miss just because you don't care about the person you're talking to. He probably just didn't make the connection that it was the same as "the girl's" bruise, because, seriously, why would he assume that they were the same person?
It's a bit ridiculous to randomly think "Hey! I think this guy is actually the girl I was just talking to even though their bodies are obviously different!" Even if the evidence was there, your brain filters out things that you know / believe are impossible.
He probably noticed the bruise but just didn't feel like it was his place to say anything + he was intent on going after the girl who just ran away after having an obvious panic attack, you know?
But of course, Inose seems to have a bit of a persecution complex, so... it's not that strange that he would assume the worst of the guy, even if he does have a crush on him.