You shouldn't use other people's things without asking them first.
Phoebe is at her friend Celine's house and needs to pick her mom up from work, but she's left her car at home.
Phoebe wants to use Celine's car to pick up her mom.
Phoebe asks Celine if she can borrow her car for an hour to get her mom.
Phoebe runs out the door and hops into Celine's car without asking to borrow it.
Celine offers to drive, and they go on to get Phoebe's mom together.
Having no idea what happened to her car, Celine reports it as missing to the police.