iPhone lost on train and its tracking now moved to 2 weeks ago instead of earlier today ?

[Schoolrefusa]

Does anyone know why this would be?
Our 14 year old left it on a train to Waterloo and had its data turned off but tracking find my iPhone was linking it to our area before it had turned off. It now links only to 2 weeks ago and does this mean anything ? I just hope it isn't in the wrong hands as we share iCloud etc and could anyone break through a password?
Many thanks for any help !

I think it must be on the wrong hands as iCloud suggests its sim has been removed and the provider's phone usage suggests calls were made from it after it was lost which is worrying as maybe it hadn't locked yet . It normally has a password

Sounds like the SIM has been removed and used on another phone. Did the SIM have a PIN set on it? (good idea, to do it next time)

I don't know why the tracking would have reverted to an earlier time

I suggest :
Remove the device from your apple account.
in future don't turn off the data if you want to find the phone.
Ensure the emergency contact details are set, or write a contact number on the back of the phone.
Enable PIN lock on the SIM
Set up legacy contacts on the Apple Account