Dog owner should know better.
You should have made sure he had a plastic bag to pick up after his dog. By no means should have been 10' into yard.
I would have rubbed his nose in it and then cleaned the dogs butt off, on the owners face! LOL!! (little humor only, do not try this at home)
Get pictures or video next time. Then stalk to find out his address. Then talk to animal control officer.
I have been known in my hood to pick it up with shovel, follow owner home then sling it onto their front door and then leave without saying a word. Everyone here thinks I'm nuts but they walk their dogs past my house really fast now!!
Good Luck!
John:D