Not written down, and so not kept. It works two ways, and they feel quite different. The first is about paperwork and history: facts, deaths, births, sales, working hours that nobody entered in a book or a system, so no trace of them survives. "Many of the deaths went unrecorded." "Much of the work done by women in that period is unrecorded." Used this way the word often carries a quiet sadness or a quiet accusation — someone should have written it down and did not, and now that part of the past is simply gone. The second is about sound and film: music, a performance, a conversation that was never captured on tape, disc, or file. "The band played the song for years but it stayed unrecorded until 1998." "That part of the meeting was unrecorded." Watch the very common pattern go unrecorded. English likes go with these un- participles — go unnoticed, go unpunished, go unanswered, go unrecorded — and it means "to happen without anyone doing the thing." It is more natural than "was unrecorded" in most sentences, and it is worth learning as a set phrase rather than word by word.