Does the absence of reply imply no opinion, laziness, no knowledge (“I don’t know about [x,y]”), no positive knowledge (e.g. thinking someone should “go x”) or/and no negative e.g. advising them “don’t go y”), a belief someone else will do it (testimonial apathy?), a belief someone else is a better informant (testimonial deprication?), a refusal to pass knowledge along (testimonial selfishness), etc.
Some of these issues are epistemic others are less clearly so (although they could probably be couched in such terms if we thought it might buy us something). Certainly there’s an empirical question – what do people say is the reason, how do they feel about not being responded to/finding results, or replying to people/not replying to them. But there’s also this theoretical space around what the possible implications are, and how technology, social roles, and socio-technic systems can address the role of silence in information seeking systems.