Hey,
there are other things that could be involved, too. You probably already thought of this but when you hear things in your sleep, sometimes they work right into your dreams. (Not that someone was scratching at your window while you were asleep), but I mean were there trees or anything near your window that could have touched the window?
I have these kinds of dreams ALOT where I hear something in real life while I'm dreaming and it works into my dream. Almost any time I fall asleep with the television on, I will have a dream about what's on the tv. I wake up, look at the TV, and go "Ohh, so that's why I dreamed that."
I fell asleep on the couch about a 4 weeks ago and my parents were in there watching television. They had a western movie on. In my dream, my mom and I were walking through Walmart. All of a sudden there was a gang shooting in there and they were shooting whoever they felt like shooting other than the rival gang. All the customers who could get away and some employees went into a back storage room where they were storing bed frames, matresses and lamps. My mom was kind of in shock so I had to drag her into the room. I asked some other people "What do we do now??" They said they would probably come back and shoot us too. I couldn't think of a way out for us and as the shots came closer to the room and the gang was closing in on the people, I Grabbed my mom by her shirt sleeve, rolled her under one of the beds, and pulled all the lamp cords out of the wall so it went pitch black and the shooters couldn't see the people.
For just a second I woke up and thought "why would I dream THAT?" Then I looked at the television and there was a shootout. lol
That kind of stuff does work into your dream..and you could have heard someone leaving their house and their door slam and hear the car take off in real life and dreamed it.
Just an idea
~Sarah