Yep, it appears that anything "before" the Big Bang is essentially "outside" of this universe and is inaccessible to us (no information available to study). But there's hopes that there will be clues somewhere (e.g., echoes in the cosmic background radiation?) Aside from that, we're stuck with mathematical concepts which may never be provable.
There are many different ideas and some proposed observational tests , for example loop quanutm gravity implies our universe bounced from a previous one. Here is a good popular article on the subject: http://www.scientificamerican.com/article.cfm?id=big-bang-or-big-bounce
and here is a proposed test: http://arxiv.org/abs/1011.1811
Of ocurse this is merely one proposal of many.
for a good starting point to many of the ideas out there watch this documentary and this book might even come out one day which will be a bit more weighty:
In short no one knows what happened before the big bang . But there are many ideas out there and not all of them are untestable. If we are lucky we might even get an answer in the next few years.
Reminds me of Comte in the 1830's:
On the subject of stars, all investigations which are not ultimately reducible to simple visual observations are ... necessarily denied to us. While we can conceive of the possibility of determining their shapes, their sizes, and their motions, we shall never be able by any means to study their chemical composition or their mineralogical structure ... Our knowledge concerning their gaseous envelopes is necessarily limited to their existence, size ... and refractive power, we shall not at all be able to determine their chemical composition or even their density... I regard any notion concerning the true mean temperature of the various stars as forever denied to us. "