AH, wait until you have dumb ass neighbors in a subdivision in which you own the house.
Not only do some neighbors allow dogs to crap in my yard but one crazy lady picks it up and leaves the bag of crap in the neighbors yard. :bs)
Yeah, I have some guy who lives down the road from me who lets his dog poo in my ivy that I've been pulling up all summer. After I stepped in a pile of it, I started watching for him & kindly let him know it wasn't cool to let his dog poop where I'm walking.
There's not a lot of things I dislike more than stepping in poo.
When I had my townhome, a angry old fat lady would yell at me whenever I had my dog off her leash, but she would let her dog poop at my mailbox. I got the pooper scooper & would fling it in to her yard from then on.
If I were you, I would collect it up & put it in his walking path to his car.
He'll step in it on his way out & if he doesn't notice it, he will after a couple min driving ;D