You are using reference points that have changed to the observer on Earth, but not to each other. If Vega was 2 degrees to the nnw of the Moon and Sirius 5 degrees to the east of the Moon, which was located at 18 degrees above the horizon due south and an outside force affected the tilt of the Earth. The Moon moves to 25 degrees due SW Vega would still be 2 degrees to the nnw and Sirius 5 degrees to the east of the Moon. Now you come along none the wiser turn on your GoTO scope focus in on Vega and Sirius and the Scope moves to a position 5 degrees west of Sirius and 2 degrees sse of Vega and finds the Moon, all is normal.