Blaise would join?? He might've wandered the train part way through, I dunno. He kinda glanced Draco over like, "HUH. You really are alive." He'd TOTALLY be able to notice Draco's appearance but he didn't say anything/react. He'd also be cool with the silence.
He usually buys some food (exception being last year), but he didn't want to give the trolley lady any gold after being slow.