Look, it's a flaw in an otherwise good movie. It should have either been better explained or the authority figures completely ignored. It was too in the middle. I still had fun and would recommend it.
It's 2025, if 17 3rd graders disappeared there would be dozens of FBI agents/podcasters/Nancy Grace-types in that area for weeks. The moment she tried to tell someone his parents had "consumption", the antennas would be up, especially if her first claim was that a man who has been around the school and presumably has friends (parents? siblings?) and is gainfully employed had a stroke two years ago and can't talk. SOMEONE would know better and call it in immediately. Adults don't just disappear. If the local police were a bunch of monkeys banging on typewriters, someone in the FBI would put it together. There's no way the parents just let it go and Brolin is the only one going deep on it.
I checked and Cregger doesn't have kids, which makes sense, because he hasn't been exposed to the viper pit that are 3rd grade parent WhatsApp groups and text message chains. That shit's for real.