The topic of unknowns has no natural "home" in a single discipline. Instead, it sprawls across a large range of disciplines and domains.  A wide-ranging survey of disciplines and domains is available in the book edited by Gabriele Bammer and me (Bammer & Smithson, 2008), with more than 20 perspectives on unknowns. You can obtain a sampler (including the TOC) of this book here. Chaper 3 in this book presents an overview of our approach to dealing with the fragmented state regarding perspectives about the unknown.

In an earlier book (Smithson, 1989) I presented what at the time was the only multi-disciplinary overview of "ignorance and uncertainty". 
This book is available as an ebook from Springer, and of course second-hand hardcopies can be found via the usual book-sellers on the net.

Ignorance studies, as a domain of its own, finally arrived in 2015 when Routledge published its international handbook on the topic, edited by Matthias Gross and Linsey McGoey. It has gone to a second edition in 2023.

       

 For a brief introduction to and illustration of what happens when domain-specific perspectives on unknowns collide, see my blog post, "Non-significance on Trial".  And a brief account of my own overview of the unknown can be found in my recent "Uncertainty" encyclopedia entry (Smithson, 2012).

References:
 Bammer, G. and Smithson, M. (Eds.) (2008). Uncertainty and Risk: Multidisciplinary Perspectives. London: Earthscan.
Smithson, M. (1989). Ignorance and Uncertainty:  Emerging Paradigms.  Cognitive Science Series.  New York:  Springer Verlag.
Smithson, M. (2012) Uncertainty. In V.S. Ramachandran (ed.) Encyclopedia of Human Behavior, 2nd Edition. Oxford: Elsevier, pp. 621-628.