Curiosity is a fundamental driver of human cognition and behaviour throughout the lifespan. Distinct from the instrumental value of information in helping to achieve a pre-defined goal, curiosity can be defined as an intrinsic taste for information itself. Although existing research has suggested a role for curiosity in enhancing learning outcomes, questions remain regarding the mechanisms underlying the curiosity-learning relationship. In the current work, we explored the interplay between curiosity, confidence, and learning in relation to the perceived "knowability" of information. Drawing on Loewenstein's information gap theory and the classical observation that curiosity is maximum at intermediate states of knowledge, we propose that curiosity is influenced by the availability of potential answers, reflecting the subjective perception of information's knowability. We conducted two online experiments using trivia questions, wherein participants estimated the number of candidate answers they had in mind for each question, reported their curiosity and confidence regarding the correct answer, and their surprise when told it. Five days later they completed a memory test for those answers. Results indicate that greater availability of candidate answers predicted heightened curiosity, moderate confidence, and enhanced memory retention. These results were replicated in a second experiment despite controlling for prior knowledge. This finding suggests that curiosity is not solely triggered by an information gap but also by the perception that information is retrievable. Our study highlights the significance of subjective perceptions of information accessibility in understanding curiosity and its impact on learning. These findings contribute to the growing body of research investigating the cognitive processes underpinning curiosity and its implications for effective learning strategies.