I'm laid up with a sprained ankle so I put my rough-and-tumble dogs out in the yard to wrestle a bit and burn off some energy hopefully. I was sitting by a window that looks out over a good chunk of the yard and saw a guy open my gate and start whistling to my puppy! Fortunately she is not the friendliest of dogs and sort of backed off and barked at him (as I jumped to my feet—ow!) and my big dog heard her and came barreling around the corner of the house. When the guy saw that he hustled back out the gate in a hurry.
I brought the dogs in and called the police, who are going to swing by soon. There have been a lot of dogs that have gone missing in my neighborhood lately and I just assumed it was coyotes (people here are dumb and let their dogs roam or put them out at night behind inadequate fencing, so...) but now I wonder if this wasn't just a one-off thing. My dogs usually aren't out in the yard unless I'm with them (except for a few minutes at a time) and my car is in the garage (usually it's in the driveway) so I'm a bit freaked out. They'd been out there for a couple of hours and had stopped playing so I think he might have not realized there was a big GSD in the yard along with the little puppy.
This is why I don't leave my dogs out there for long unless I'm directly watching them. There's just so much that can happen, even in a safely fenced yard.
ETA: Cops just left, they took a report and are going to compare it to any other reports and also keep an eye out for someone matching that description. I know one of the officers who came pretty well (we've spent a day hiking through the woods together as part of a search mission) so that was nice. They weren't here long (10 minutes or so?) but at least I made a report I guess.