Early on Friday evening, hanging out at a bar with friends, Boon Sheridan downloaded Pokémon Go, the new augmented-reality iOS and Android game.

Pokémon Go forces players to wander through the physical world around them—streets, parks, and public spaces—to catch Pokémon. Players can also assemble near certain structures, like churches and pieces of public art, to battle their Pokémon against computer players at “gyms.”

Sheridan is a designer living in Holyoke, Massachusetts. Being of sound heart and mind, he quickly caught a Squirtle. But then he put his phone away. It was Friday night, after all. Yet getting home in the wee Saturday hours, he remembered to check into the game and noticed that there seemed to be a gym right over his house.

“And I thought, that can’t be right,” Sheridan told me. Then he fell asleep.

Sheridan lives in an old renovated church, built during the 19th century. The next morning, he woke up and shuffled to his kitchen. While gulping down glassfuls of iced coffee, he stared out the big window to the park across the street. And then he saw them: A handful of strangers, all standing on the sidewalk in front of his home.

“Have you ever seen people standing near each other, but it’s clear they’re not with each other? That was exactly what was happening,” he says. Some were leaning on his fence, others milled on the sidewalk. But they were all looking at him—“looking at the church, through their phones.”

His phone hadn’t made an error the night before: Sheridan’s home really was a gym. Throughout the rest of the day, about 40 more strangers showed up to hang out in front of his home. Without giving his consent or having any forewarning, Sheridan’s property had become a virtual neighborhood landmark.

Sheridan, who works in technology and knew about Pokémon Go, handled the newcomers with aplomb. But his experience raises difficult questions about how augmented reality will jell with, well, pre-existing reality. Especially because no one right now seems to know where Pokémon Go’s description of reality comes from.

Pokémon Go is essentially a maps application with a gaming layer. At its heart is a map of the player’s real-world surroundings, the neighboring streets and landmarks providing both its environment and its obstacles. But since its release, it’s become unclear where the the geographical data that describes and defines those streets and landmarks is coming from.

As my colleague Ian Bogost writes, Pokémon Go closely resembles Ingress, another augmented-reality mobile game produced by Niantic Labs. Ingress players collected data about local attractions on behalf of the game. Some Pokémon Go data seems directly taken from that Ingress haul: Portals in Ingress have been transfigured into Pokéstops.

But it’s unclear if Ingress provided all the data used by Pokémon Go. And no one seems sure of where the underlying map of streets is coming from. Street maps are serious—and expensive—business. Nokia spun off its mapping-data team as a separate company last year, valuing their work at $3 billion. And OpenStreetMap, a free and open Wikipedia-style map, supports a network of smaller mapping startups, some of which have raised tens of millions.

Niantic itself was spun out of Alphabet, née Google, last August. This would suggest that Niantic’s underlying street map and geographic data comes from Google’s own mapping team. But the game’s in-app page of legalese doesn’t mention any source for the mapping data, though it does say that Pokémon Go licenses from other Google products like Android.

That’s odd, because most digital maps insist that apps cite their license when they use them. Even OpenStreetMap, one of the most complete and permissive databases of geographical information, mandates users “credit OpenStreetMap and its contributors.” Pokémon Go could, however, have used a limited and imperfect U.S.-government map called TIGER without citing its existence at all.

Niantic representatives cooperated with my requests, but they declined to answer where data in Pokémon Go comes from. I’ll update this story if I hear back from them.

Sheridan is not the only person who awoke one morning to find his home had been transformed into an enormous Poké-gym. After tweeting about his tale, three or four more people across the United States contacted him to say that their homes—which were also former churches—appeared as gyms in the game too.

His property has effectively been augmented by a digital beacon—a distinction that sends about 75 strangers to his front yard everyday. For him, Pokémon Go’s use of geo-data seems like a standard example of an easy engineering fix having massively unintended consequences. Even if the game just uses Ingress’s dataset, it fundamentally changes the nature of the data to expand its user base from a couple hundred thousand users to millions and millions.

“What Niantic did is they collected a lot of data and then they radically shifted the context in which that data was used,” he said. “I’m not sure I can say whether it’s right or wrong, but it makes me feel really squishy. All these people—there’s the potential for some of these locations to be flooded with strangers overnight.”

Sheridan wonders if any project manager ever asked: “Are we cool with this? No releases were signed. Was this database managed? Was anything done to negotiate the shift in context that was going to happen?”

On Sunday, he handled his life as a “living edge case” by taking his gardening tools to the front yard and trimming some plants. Then he could ask the players, “Hey, are you training?” and introduce himself to them.

Most players geeked out to think that someone could live at a gym, he said. “Oh my god, that’s so cool, you don’t even have to leave home!”, he reported one of them saying. And he did seem clearly delighted to find his own real estate suddenly augmented by a kind of virtual reality. Sunday afternoon, he asked a group of guys if they were training.

“Heck yeah, this is my gym,” one of them replied. That meant that the game had declared him the gym’s “owner,” the best player who had visited the location. His real-world avatar seemed pretty into Pokémon, too—he was, Sheridan later tweeted, wearing a Pokémon belt.

“Cool, this is my house!,” Sheridan said. “We should be friends.”