Visible crew/equipment: When the Ogri does attack the Doctor and Rumford in the cellar, the person pushing it is quite visible as is another crew member standing to one side.
Revealing mistake: K-9 has a bit of difficulty in the mansion in episode two. The thread pulling him is visible and Baker has to help him over a flagstone.
Continuity mistake: After the Doctor helps Romana over the cliff, the stock footage of a sun setting over a calm sea does not come close to matching the total darkness and stormy seas in previous shots.
Answer: It was never destroyed on-screen; it was intact at the end of the TV movie, and destroyed by the start of the 2005 series. It was destroyed in the novel "The Ancestor Cell," but in a completely different manner to what happened in the series.
DaveJB