You seem to be missing the point:
As above, why do insurance companies ask where the car is kept, garaged, driveway etc If it doesnt matter, whats the point in asking?
Of course they will pay out its nicked from outside a mates not the registered kept address, but that is a completely different thing from if its nicked from your home address and you have said its NOT kept there and as you say they ask the neighbours and all confirm the car is always kept there, you will definitely have some explaining to do. As you say in ever other insurance related thread, dont give them any excuses not to pay.