Conveniently, she's saying that she left her phone at home... So red flags indeed...
"Stauch admitted that she left her phone at home on January 27, but said she had an Apple smartwatch on the entire time, which can easily track her whereabouts."
Gannon Stauch stepmom reveals where she went the day Colorado boy disappeared [EXCLUSIVE INTERVIEW]
Edited to add re: Apple Watch tracking when your phone is not nearby - "Keep in mind that Apple Watch does not have built-in cellular capability, so it cannot be located when it does not have access to a trusted Wi-Fi network. Location sharing also depends on factors including the watch being turned on and having sufficient battery charge." Not sure if that's model dependent, may not be accurate for whatever setup she had going on...
GPS to Track Loved Ones - Apple Watch - Apple Community
Edited to add again because now I'm angry thinking about it: She has an expensive smartwatch. Yes, let's tell Gannon we need to sell the SOFA and not, you know, your iPhone or Applewatch... WHAT A TERRIBLE HUMAN, obviously for so many reasons, but the details like this really get me.