SS is an adult. When her mother didn't get in touch with her, she probably didn't phone LE immediately. When Mom did phone LE, and report her missing, again, b/c SS is an adult, there is a 48 hour window, before SS would really be considered missing.
I think SS's mother was concerned, but, maybe thought that SS hadn't woke up yet, and was hoping to wake her in time for her to get to her court date. It's another reason, I think, that folks didn't worry so much at first... some folks, if they've been using/partying & out all night, will skip a court date. It's either show up looking like death warmed over, or hoping to beg off and get another date set. Worse case scenario, someone has to bail you out of jail after a couple hours, if they snag you on a warrant.
If she was willing to go to GC, at 3:00 a.m., mom probably already knew that SS was gonna be hard pressed to make that court date.
Had Mom's last phone call with her been one of SS being in distress, it would have been looked at immediately by LE, and been on every news station. Close to 2 1/2 days probably lapsed before much investigation started. So Jan 6/7th before the word really gets out that she's even missing. Jan 9th is when the truck was spotted in GC, heading toward Richmond, (same day I heard about the case, and through a friend at that). Jan 22nd, the white car is taken by LE, and the Cauc male's, parent's, home and property are searched. The rest is a mystery.