Sock fell down lint vent and daughter turned on dryer

Turn off you power to the dryer and then,
You could run a coat hanger straightened out with a hook bent on the end of it into the lint vent at try to hook the sock.
But probably you will have to remove the back to follow the lint vent.
You may try to remove the vent hose and run the straightened coat hanger in there to try and remove the sock.
Hope this helps