Continuity mistake: When the Doctor shoots Stor with the De-Mat Gun, the flash starts on Stor's left-hand side, engulfs him, then jumps substantially to the right before whiting out the frame.
Continuity mistake: The Doctor has his scarf when he first meets with the Vardans. When he returns to the TARDIS, it is on the coat rack.
Answer: TARDISes are generally available for properly authorised use on Gallifrey; they're not usually assigned to a particular Timelord on a long-term basis. The Doctor stole his when he left his homeworld.
Tailkinker ★