This paper problematizes the assessment of speakers' proficiency in endangered language communities. We focus in particular on processes of lexical production and elicitation as proxies for full proficiency assessment. Among linguists, it is standard to assess a speaker's knowledge of specific lexical items in order to set a baseline for further data collection and research. Yet, as we argue in this paper, such tests can give the false impression that speakers do not know their language, since such tests do not distinguish between what speakers can recall in a particular moment and what they do not know because they did not acquire it. The endangered language context in particular calls for a more fine-tuned interpretation of lexical knowledge, given the high degree of idiolectal variation and lack of a community-based standard language. Drawing on fieldwork with Chukchi and Even Indigenous communities in northeastern Russia, we analyze lexical items that speakers claim to not remember. We then distinguish different reasons that are given for not remembering and consider their implications for speakers' proficiency. Finally, we conclude with two recommendations for improving elicitation and language assessment tests.