The censor line was a Scorsese arty trick. The narrator, Henry Hill, is getting extremely paraqnoid. The censor line prevents you from seeing the number that Lois called. I think it emphasises Henry's obsessive paranoia at that point - he (and the director) doesn't want you to see the number.

The stuff in the alley was "dresses". In real life, it was actually t-shirt material. Karen really did freak and run in real life.
If you look carefully at the scene you can see men unloading boxes in the alley - so probably Karen was just being needlessly paranoid.