Re: the other planet
I thought about it too, Marcia.
It's been some time that the scientific community has accepted the large impactor theory, forming the Moon.
This was 4.52 Billion years ago
The Moon seems to have strongly been impacted 3.9 Billion years ago (thus 1.58 Billion years after the creation of the Moon).
Could the ejecta left from the first impact have wandered chaotically for so long?
Is it a long time or not? We don't know.
But the ejecta couldn't have gone very far and must have remained in the inner solar system (perhaps an asteroid belt within the Eearth-Moon system, around the Sun).
Raoul