Re-homogenizing the Earth-Moon system
Moon was produced by a head-on collision between Earth and a forming planet UCLA-led research reconstructs massive crash, which took place 4.5 billion years ago
by Stuart Wolpert, UCAL Newsroom, January 28, 2016
Are we getting closer to understanding where the Moon actually came from? Los Angeles times
Young1, E. D., I. E. Kohl, P. H. Warren, D. C. Rubie, S. A. Jacobson, and A. Morbidelli, 2016, Oxygen isotopic evidence for vigorous mixing during the Moon-forming giant impact. Science. vol. 351, no. 6272, pp. 493-496.
It seems like this event would have scattered bits and pieces of Theia and pre-impact Earth into space where
they would drift about in space and eventually come back as meteorites.