I went back to Sami's statement, and the statement Placer County Sheriff's Office put out:
Sami: "At about 12:36 a.m. I saw a call from her, so she called me. I was on my way home from the party and I was... she was supposed to give me a ride home, but I'd already told her I didn't need a ride home. And I answered it and she said, 'hey where are you? do you still need a ride home' and I was like, 'no I already told you this, we're all good. I'm like in the car right now like, thank you so much' and she was like, 'yeah course, love you, goodnight, like, I'll see you tomorrow' and I was like 'ok, love you, see you tomorrow, be safe' and then after that nobody's had any contact or sighting of her. So, it's been complete radio silence, her phone has been off, her like, location isn't on and nobody seems to have reportedly even seen her after 12:30 a.m., so." (Sami Smith interview with Fox 40)
PCSO: "She was last seen at the party on August 6th, 2022, at approximately 12:30 a.m." and "Kiely's phone has been out of service since the party." (per Facebook page)
So no exact time on when the phone was turned off.