It is correct that on trading there is nothing loss until it is panic sell but if the price drop too much and it goes to to below and don't recover then it remains loss though it is not sold. Also there is no way to recover for example ,if we consider about the luna than it will be clear about the loss without selling. Though the value is not 0 but it is near 0 and there is no chance for recover.
Until the coin is sold, it should still not be considered to be a total loss but can only be said to be a reduction in portfolio value. If we are to talk about the Luna crash, I will say it's a complete disaster. Not only do most of them lose their investment, but they were also affected mentally, which will be hard for some to recover from. The coin is in its dying stage; no matter what's keeping it alive for now, its chance of recovery is very low.