Hello, If the player never did a mystery gift, a default trainer can be met in the Trainer House located in Viridian City (with the highest evolutions of the threee Johto starters). But if a player did a mistery gift, the default trainer is replaced by the party of the latest player connected for a mistery gift. Some research has been done about the Trainer House (located in Viridian City) and the offsets in the save file. See here. It'd be awesome to have a feature in PKHeX