Big House Problem

When more than one person is over a house that is vast in size and one eventually leaves without the other because they assume they've already left due to the fact that they haven't run into each other in awhile.

George: "oh, you're still here!"
George" "your friend took off, she thought you left, so..."
Girl: "really?"
George: "that's what happens in a big house. It's called the big house problem."