Agreed. This is actually the first thing that got me interested in the case also - it stood out to me immediately as odd that she was reported missing so soon by the boyfriend. It's never really been explained, we just speculate as to why his worry escalated so quickly.
If the scenario we follow is his innocence and truthfulness with police, then perhaps he did hear about the fight through the grapevine. Supposedly the fight was ZO's concern over LS's condition, by some accounts. Perhaps witnesses to the fight (or those overhearing the fight, or second hand accounts) got in touch with him quickly. The next morning, he searches, can't find her, realizes phone is at Kilroy's (either picks it up or doesn't, unclear) and deduces through friend's account that she is in danger, calls parents and LE report is filed (by him? By two female friends we rarely hear about again? Also currently unclear.) <snipped>.
You know, I also initially thought it was odd that Lauren was reported missing in such a short timeframe. But as more details of the timeline came out, it because less odd to me.
By noonish, JW had gotten a call that Lauren's phone had been left at the bar, and he and her roommates started calling around looking for her. Keep in mind, there were quite a few witnesses to what happened the night before -- there's no doubt at this point, if they hadn't already, they would have heard about the altercation. They also would have heard the descriptions that we've since heard from witnesses in the media and in the lawsuit docs -- that when Lauren was last seen, she was incapacitated and incoherent, and being dragged home by Corey Rossman, an acquaintance of one week. They would have heard that he was acting 'aggressively' and 'inappropriately', and that when people told him to bring her home, he told them to eff off and left with her.
By mid afternoon, calling around, HT talked to JR and he told her that Lauren left at 4 am to walk home. Going by the other witness statements, it sounds very possible that around the same time, others heard conflicting stories from CR and MB -- for ex., the witness at CVS, who was described as a 'friend from smallwood' said that MB told him he watched her walk out the door towards home. And then there are the other conflicting witness statements from neighbours that may or may not have taken place this afternoon. It's always pointed out that it's possible these statements had some details mixed up as they were reported. Maybe. It's also possible they were reported accurately. A few of those witness stories make it clear they found the stories suspicious -- For ex. the witness at CVS and the neighbour who reported Corey "looking for a little blonde girl" both make a point of saying things that raise questions about Corey and Mike.
So yeah, under these circumstances -- If my roommate didn't come home, I was told she was last seen being carried home half conscious the night before by some guy she had just met who was acting aggressively and now claimed to have "amnesia"? And then the stories of the last people with her didn't really make sense? And even still, according to them, she left at 4 am with no phone, purse or shoes and hadn't been seen since?
I would call the police too.