Individuals of European ancestry, such as those making up our sample, possess only a small fraction of the total genetic variation in the human population (1000 Genomes Project Consortium, 2012); Africa alone has more genetic diversity than the rest of the world combined. There are myriad examples of genetic effects that are largely limited to specific ancestral or founder populations, and the absence of a significant finding in a European sample does not preclude the discovery of a large-effect variant identified in a different ancestral group. This is especially true for rare variants, where ancestral divergence is the rule.
