Its been years since I read the novel, but if I remember correctly the event of them passing each other by wasn't written until later, with a flashback in Roxy's point of view. Could be wrong about that, though.
For those saying its stupid they passed each other by, remember that its a crowded street with a constant flow of people, neither of them spotted each other and were preoccupied talking to their companions. Although Rudy did think he heard her voice, it was basically a murmur in the buzz of a city, and his knowledge of her being two continents away and having duties tutoring royalty dispelled his thoughts of her actually being that.
Btw, dude in the alley really wasn't a pedo, he's seriously a kindhearted guy that wanted to provide food.