Zach will nod giving a bit of a sad look. "Yeah I hate that." And then he'll smile. "I'm glad you like it. If you ever can't find me and need me. I'm likely here."

Yeah, Logan will still be worried about her even though he is sneaking over to see her because she's still doing that. 

So Logan is very happy by the way that Clary is in the lunch room and didnt really even hear the fight. Just going to hear the rumors.