Seen in Pensieve?

In the appearances section, it says that Horace's Slughorn's first office appeared in Deathly Hallows: Part 1, seen in the Pensieve. But I wonder... how? The Pensieve wasn't even in Part 1, so how was it seen in it? If you mean in Harry's dreams at the Burrow and at Grimmauld Place... the office weren't even seen in those! Only Slughorn's voice is heard from the memory, but the office itself is never seen. If someone could figure this out, it would be helpful, since I do not wish to remove it quite yet if it was indeed in DH: Part 1. AlastorMoody 22:21, September 30, 2011 (UTC)