In this study, we share our broad and deep search for what is known from blind-peer-reviewed research publications about the efficacy of the instructional practice of Number Talks. We describe our process for literature review and the subsequent analysis that revealed a shallow depth of articles for which one can discern the factors of quality of Number Talks, as an instructional practice, taking place in K-12 classrooms. Further analysis revealed a new construct for researchers to consider which we call a Black Hole of research on instructional practice. We explain the meaning of a Black Hole using Number Talks as a case example of the phenomenon, which occurs at the intersection of research and practice. Implications for the future of research and teaching practice are discussed. Many areas of possible research are illuminated.