The, uh... the wagons are now deceased.
I've never seen this in my life. I'm not sure if it's a bug in the game, or what. What I am sure of, however, is that there's a lot of unclaimed stuff just kinda strewn about on the ground there now. Just lying there on a pile of lumber that used to be Urist's wagon. I have the option of having my dwarves claim it. Seriously, take a look at all this shit:
Click to make it bigger. I circled in orange where the wagon fell.
Look, I know these are fellow dwarves, and not elves, but what am I supposed to do? Let the kobold thieves take it? I don't see Urist struggling to get any of this shit back. He's just standing there staring at it like an idiot. Hell yeah I claimed it! Praise Armok! We'll never go hungry again! Weapons, clothes, armor, food!
I wasn't able to do any trading at all. Three of the four merchants of Kastolvutok were already at the depot, along with my broker, Mistem, but I still couldn't trade. They were waiting for their wagon to arrive, I guess. Probably standing around making awkward small talk with Mistem. "I wonder what's keeping Urist? He's got all our stuff. I'm sure he'll be here - with our glorious bounty of goods - any minute now." I mean, don't get me wrong... it's not like I feel bad or anything. But Urist has gotta be in some deep shit with his bosses.
But at least now I have some metal! Here I come, Bomrek!