He leaves the alley feeling more than confused and just a tiny bit angry. Sure, he's not from the best part of town and he doesn't have the greatest job, but never in his life has he felt as worthless as the girl who's supposed to love him just made him feel. How could she just run off with some alien she just met and leave him standing behind, looking like a fool?
It takes him a while to get back to Powell Estate. It's as if his feet suddenly forgot the way, and rather than remind them, his brain was too busy thinking other thoughts. The sun is just beginning to peek over the horizon when he finally falls into bed, where he stays until the sun has completed its arc and begun anew and Jackie Tyler comes pounding away at his door.
He tells her that she's probably over at Shireen's, that he hasn't seen her since two days prior, but Jackie's back soon enough, demanding furiously to know where her daughter is, since Shireen's denied her ever being there. What is he supposed to tell her?
The next year is the worst of his life. She's gone missing, and whispers of kidnapping and murder follow behind him whenever he walks down the street. He doesn't know what he's supposed to do. Would anyone, if they were in his position?
So he does the one thing any concerned, angry, and let's face it, slightly jealous boyfriend would do: he does his research on the man who showed up out of the blue to whisk away his girlfriend to see the sun and stars. He needs to dig deep to find any information, and he discovers he isn't so bad at this computer thing. Maybe, just maybe, he isn't as worthless as she's made him feel.
But then they're back, and he's back to feel like the third wheel, the shadow. Until he's the one saving the day, with those computer skills he'd picked up in her absence. And even now, he's still not enough. Somehow he's never enough when they come around.
Until he stops waiting for her. Until he decides he's going to travel with them because he wants to see it for himself, not because he needs to be with her. Until Sarah Jane Smith and her dumb tin dog show him that he's worth something, that he's good for something. That Rose isn't perfect, and he shouldn't be holding her up on the pedestal he's put her on throughout their entire relationship.
So when he drives off in that van next to Jake in a world similar to his own but entirely different, he's grown into that man he'd wanted to be for Rose, but now he gets to be it for himself.
And when he sees them again, a while later, he can enjoy it, and not feel like such a shadow.