Recent debate about the reliability of psychological research has raised concerns about the prevalence of false positives in our discipline. However, false negatives can be just as concerning in areas of research that depend on finding support for the absence of an effect. This risk is particularly high in unconscious learning experiments, where researchers commonly seek to demonstrate that people can learn to perform a task in the absence of any explicit knowledge of the information that drives performance. The fact that some unconscious learning effects are typically studied with small samples and unreliable awareness measures makes false negatives especially likely. In the present article we focus on a popular unconscious learning paradigm, probabilistic cuing of visual attention, as a case study. Firstly, we show that, at the meta-analytic level, previous experiments reveal positive signs of participant awareness, although individual studies are severely underpowered to detect this. Secondly, we report the results of two empirical studies in which participants' awareness was tested with alternative and more sensitive dependent measures, both of which manifest positive evidence of awareness. We also show that, based on the predictions of a formal model of probabilistic cuing and given the reliabilities of the dependent measures collected in these experiments, any statistical test aimed at detecting a significant correlation between learning and awareness is doomed to return a non-significant result, even if at the latent level both constructs are actually related and participants' knowledge is completely explicit.