[Fey]

Okay, I've read this a few times and I hate to say it...but I don't think it was an attack. Yes, if you're wary of dogs it would feel like one, but I actually think the dog was trying to encourage you to play with it. I've worked with animals for 10 years and was 'raised' by them for the years prior to that. Often dogs will bark and growl to get your attention, 'asking' to have you interact/play with them. When you bolted for the door it probably thought you'd started a game of tag(part of why you never chase a loose dog). When you stopped and didn't do anything it figured you'd given up the game, hence the sniffing about.

Am I saying this wasn't aggression on the dogs part? No, I wasn't there, can only surmise from what you've said, but I've been around enough animals that's my first, third and fifth thought after reading it. Should you assume all dogs doing similar things are playing and not protect yourself? Heck no!

That all being said I would STRONGLY recommend talking to the neighbor that owns the dog(or have a friend/parent/someone if you're not comfortable about it) about having their dog loose. Most places consider that a violation of the leash laws, and if the dog SHOULD attack they can be charged with up to Assault with a Deadly Weapon(friend got served with that, we laughed even as we realized how serious it was). If you continue to see the dog out and about loose call your local ASPCA and report them, they'll talk to the owner and issues fines if it continues.