There are many reasons why that can happen.
- The spacing between the words might be wrong, and I’m fixing the spacing line by line, sentence by sentence, before focusing on the lesson itself. Sometimes I might even try to pretty things up by putting the end-of-quotation marking on the same line as the actual sentence being quoted rather than over in the next sentence all by itself.
- The audio might be mis-matched, and I’m editing the audio start/stop times for each sentence in the lesson editor prior to studying the lesson.
- I’m paging through to make sure the whole lesson is there.
- I’m going through and making note of the sentence number where each new chapter begins (in a short multi-chapter lesson) because there’s no other way to get to the beginning of a particular new chapter to just re-study that chapter.
- I’m pre-reading the lesson to see how much meaning I can pick up from context without looking up the words, and planning to go back through the lesson and lingq the vocab, but oops, they all disappeared.
- I’m paging along while pre-listening. If I lose my place while listening, I might page right multiple times to find the right place that matches the audio (please remember that this is not my native language!!! It’s easy to make mistakes!!!), and suddenly, oh, oops! Did it again! Marked lesson as complete! Kicking self big time.
- For those making flash cards, a person might only want to lingq the words that they want to use as flashcards and have show up in the review -actually this got so messed up that I don’t even use the flashcards or review sections any more, since a word can only be either known or lingq’d, and not “saved for later” or status zero, which is what one would hope blue would be. I don’t want unfamiliar words marked as known and added to my known count and un-highlighted, but I don’t want a huge ton of flashcards of words that I’m not yet planning to focus on learning, either. But even without that, back when I was using the flashcards, that wasn’t working very well for multiple reasons. Some of those bugs may have been fixed by now, I don’t know. (Completely unfamiliar sentence with missing word, what could it be? Blank flashcard, type in your guess as to what could be on the other side? etc.)
An un-highlighted word should mean that I actually do know the word. Otherwise I see an un-highlighted word while reading and I stop a minute and say, wait, I should already know that word, right? it’s, umm… it’s… nope, got nothing.