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.