The same thing happened to me, which I caught on camera and shared with my neighbors on Nextdoor. Very quickly the people along my street identified the address of the "poopetrator", and soon made a habit of tossing his poop bags back into his yard. He moved away a few months ago, so fortunately I've had no "gifts" in plastic bags wind up in my front yard as of late.
One interesting "old school" tactic that came up in the Nextdoor discussion: if someone's dog keeps pooping in your yard, and that person refuses to clean it up, just pour bacon grease over the poop. The next time the dog visits, he'll clean up his own mess. It shouldn't take more than one or two such treatments before the dog's owner learns to steer clear of your property.