It is November 1980 and Detective Wayne Hays is looking through the room of a missing boy. He sees two books: "The Official Scout Handbook" and a hard-bound Advanced Dungeons and Dragons game book titled "The Forests of Leng". The AD&D book never existed (possible story clue with "Leng" reference?). Also, the TSR company logo and AD&D font on the spine of the book were not adopted until 1982.
Detective Wayne Hays states he remembered the night of the disappearance of the children very well. He stated it was the date Steve McQueen died and there was a bright full moon.
Steve McQueen died on November 7, 1980, and there was a dark, new moon on that night, not a full moon.
When Tom Purcell is working on his car in his driveway he is listening to music as his children leave for the playground. When he realizes they have not returned after dark, a baseball game can be heard on the radio. Given that it is November 7, 1980 and the World Series ended October 21st, there would not have been an MLB game available for broadcast.
The reflectors on the Purcell children's bicycles are a later 1980s type. In 1980 the mounting hardware on those reflectors would have been metal, not plastic.