You didn't know the Winchesters. Just like everybody else in this god forsaken world, they were nothing more than either somebody you don't know, or mass criminals with and unbelievable history. Thankfully for you, it was the former, so when they show up in the middle of what you're doing in an alleyway(as if that isn't an odd thing to be doing), you don't think much of it. Just some people passing through; that happens sometimes. Nothing to worry about.