Since the magnetic field outside the solenoid is negligible, it is impossible to detect current in the solenoid from outside.
Suppose I put a conducting loop of large radius, say, $10^9 $ km around this solenoid.
Then according to faraday's law an emf will be induced in the conducting loop when we vary the current in the solenoid. How is this possible? There is no way for the conducting loop which is far away from the solenoid to detect the flux change inside the solenoid, right?