Because that Saturday was the 50th anniversary special, and they had to give it back, I’m guessing.

Transcript:

Mr and Mrs Bugg are standing on either side of an antennae’d police box, with a bank of windows near the top of the doors and a light on the roof. Mr Bugg is rocking a fez and a bow tie, while Mrs Bugg is resplendent in her normal bow. They are both gesturing grandly towards the police box.

The text reads: “Come play in our Tardis … until Saturday.”