Did you not offer to go over and collect it from where he is? On the basis of what he has now done, did you tell him you were reporting the matter to the authorities. Also, try and record any conversation you have with him
Team Taxi here.
He isn't keeping the passport and if your son was desperate to use it then he had today to sort out paying the driver. You know your son and therefore that it was a genuine error but the taxi driver doesn't.