I liked Buddy. I did notice that he sure understands a lot of human speech for a dog, but that’s not totally impossible, and it also common in fictional animals. The story is interesting, and I really felt for poor Buddy.
I was glad when he ran away from Robert in the end. I did wonder where Buddy was going to go, although I am not sure if it really matters. I was a bit confused when Buddy thought of Robert as being the worst person a dog could get, because he seemed like a good dog human, although still a bad and criminal person. Of course, Buddy probably does not realize that could have ended up with an abusive dog human. I am still kind of glad that Buddy still left him, even though he was a good dog human (I know the term might be a little silly, but I just do not like to refer to myself as my dog's owner), and even though he probably does not realize how good he had it.
I think this might have been more exciting if I had not known, before reading it, that he was going to find out something bad about his human, and it had come as a surprise. Still, I do understand that you had to put something in the logline that would make people want to read it.
The scenes at the park were confusing because of the way they were all together. You might want to at least separate them into different paragraphs, or into separate scenes, which they seemed like they probably should be. It would make it neater, easier to read, and more like how an official film script in formatted.
If you have a scene in the same place, during the same time of day, as you did earlier, you might want to add that it's later. I am not completely sure why this is, but it probably prevents confusion.
Example:
EXT.PARK-DAY-LATER
Scene
Also, when a character is on the phone, you can put it in the same line as the character’s name, as long as it is after the name.
Example:
ROBERT (on phone)
Dialog
Also, there is a small issue with the flashback on page eight You told about it in in the script, to somebody reading the script, but now to somebody watching the film. You might want to add a scene showing the flashback.
Example:
FLASHBACK
SCEAN HEADING
scene
END OF FLASHBACK