He nearly repeated the comment or offered some variation on it because that wasn't a very smart thing to say. Wondering didn't really help any, but then again harassing Anthony Goldstein, who for better or worse, seemed to be his accomplice at the moment, didn't help either. The alley. That was what he was supposed to be focusing on and not the fact that he was the big question hanging between them.
And what came next was not what one would expect from Zacharias Smith, the great flee-er of the Battle of Hogwarts. "Well, there would only be one way to figure that out." At the moment he finally seemed to be considering going over there, something shift. Maybe the spell changed or was weakened, but it wasn't quite the same anymore. It wasn't such a struggle or an immediately bad idea to look.