Let's think about the timeline and where the parents should/do become concerned.
Seen by mom early morning Monday, as far as she knows AJ has no plans for the day. Assume mom works until 5 or 6pm, comes home, younger sister says AJ is with friends. Perhaps some texts go back and forth between Mom and AJ that no, she won't be home for dinner, she'll be home later, etc. Mom goes to bed before AJ is expected home. At some point early she wakes up, realizes AJ never came home, texts her saying where the heck are you? And AJ replies that she is not ready to come home yet. Tenor of those texts are off, can't get ahold of her, no friends know where she is, worry mounts and mounts and family and friends start social media outreach push early afternoon. MP report filed that evening at 9:15 pm.
But in that case the worry starts on Tuesday, NOT the night before.
So if they were worried and unsure what to do the night before, as WH states, then SOMETHING happened Monday that caused concern BEFORE the suspicious texts Tuesday morning.
Does that make sense? I have a terrible head cold, lol, so sometimes I don't even make sense to myself!