Caroline is a mumsnetter and has decided it's easier to just buy a new car and never, ever go back for the old one.
Yeah, I suspect this could potentially be true ...
Or, she has now seen that the coast will be clear when the OP goes for her appointment and will dash in and retrieve the car then.
Unless this is all An Evil Trap and the OP is not, in fact, going out but is sending a stunt double in her place, while she waits at home to yell 'SURPRISE' as Caroline sneaks in to get her car (possibly dressed as a penguin).
I'm waiting for the 'reverse' thread called 'I only parked there for 10 minutes and now I am the talk of Mumsnet ...' or 'I need a new car urgently - anyone know a good deal?'