Didn't it look like the sleeping bags had blood stains, maybe from bullets or stab marks. My guess is they were ambushed and their supplies taken. Probably one of those that will never completely be explained though.
As far as the van, the preview clip at 2:23 shows it falling off the bridge with no walkers around it. no big news, just an oversight, and it was so quick, not many would notice. But it does show the van definitely would have gone down nose first and either continue straight down or land upside down...
My little gripe was that they are in this nice office that looks like it hadn't been touched. First I would go through all the drawers, then I would make sure I took the rest of the water somehow. Daryl says fill up, then they each take a drink and walk out, at least drink and then re-fill....I actually don't care about the little details, but this one stuck out to me.