what just happen to Uryuu??? Was his arm cut off? It looks like it

Well, while I think it might be hilarious if his arm is in an oddly shaped hole in the street, or if it's somehow tucked behind him and that's coffee he's lying on, it's pretty likely that that's blood and that's the place where his arm should be. That's probably more likely since that image next to him looks like a siren. Oh but don't worry. They can regenerate organs in Soul Society, I'm sure arms aren't much of a stretch, Yamamoto probably has his back already.

I am pretty sure his arm got cut off, but as previously mentioned, either the soul society or Orihime will fix it