Wonder if he hit anything? I would jack up one front wheel at a time and check it out. Could be brakes, Bearings sticky caliper with worn down pads. you kind of have to look to eliminate possibilities.

If you push in the clutch or put the automatic in neutral when underway letting off the fuel pedal and the noise does not stop or change . It is probably not the engine or transmission.

Consider yourself lucky you did not loan him your girlfriend.