There's something I feel like I have to explain. When I hesitate to find a word in Chinese or Korean, a lot of the time it's not because I didn't learn the word. It's because it's not on the tip of my tongue (somehow not easily accesible in my mind). So I find it weird to think that if a student can't retrieve the word, that the assumption might be that they never learned it. Don't you have situations even in your native language where you can't think of a word until someone else says it? I do this in English a lot and it's my native language. So the fact that I do this even more in other languages that I'm learning isn't surprising to me, but it's surprising that other people take it to mean the information isn't there at all.