Dean swallows hard, nodding in that way which says I know where you're coming from as the kid rockets through her story, his mouth going sandpaper-dry when she gets to the part about being 'supposed to'; you don't forget what it's like to be nine years old and have little brother who's not where he's supposed to be when you just took your eyes off him for a second because he was being a dick...
Then she mentions that other kids are missing. Dean wonders vaguely why none of this has made the papers; the only reason he can think of is that the news hasn't broken yet, which means loads of kids going missing in the last day or so, and that really isn't good, and he's talking over Sam - “Maybe me 'n Sam could come talk to your mom? Because she's probably really worried about where you are” - and shooting him a sideglance, a silent yeah, definitely a case (along with a more incredulous goat-monsters? ' the hell? because Sam's pulling that face which means it's struck a chord somewhere in his Encylopaedia of Weird and... seriously, goat-monsters?) as he's working out what story they can use, what cover doesn't need IDs and uniforms and things he didn't think to bring with him because 'normal civilian barman with a girlfriend and an apartment' is already a coverstory in itself.
“Whoops. Uh. Sorry Sam. You want to take this from here?” He turns his attention back to the kid. “You think you could tell Sam here everything you know about this goat so he can figure out what sort of monster it is?” - and he's got a vague memory (which isn't really vague at all; any time anything bad happened to Sam is always crystal clear) of refusing to tell a 'nice cop' anything about his missing brother on the grounds they were a stranger (and the fact this girl doesn't seem to have any such compunctions has the big brother in him worrying about her as well now) and belatedly sticks out a hand, halfway between 'shake' and 'hi-5' - “I'm Dean, by the way. What's your name?”