To quote Dana Mackensie, author of 'The Big Splat': Or How Our Moon Came To Be' -

"Science proceeds by analogies and by reproducible experiments - but there is only one Moon, and no laboratory will ever be large enough to produce another. Moreover, planet formation ( which includes moon formation ) isn't exactly the province of any one science. Geologists can tell how a rock forms, but they can do so only if a context for a rock - a planet - already exists."

This is my point, I believe the data that suggests the existence of Theia is being placed and evaluated in the wrong context - i.e. that planets form primarily by accretion and retain constant diameters ( see: About This Site, page 2, for the hypotheses )

On later Moon missions astronauts were trained to look for what geologists called 'genesis rocks', rocks that date from a planet's birth and which contain scientifically un-contestable physical and chemical evidence of the conditions under which they were formed. The information these rocks contain, however, can be judged in the wrong contexts just as easily as their earthly counterparts. In the following sections I will try to put together an overview of these 'genesis rocks' as revised within the context of this website's overall hypothesis.