I have lost a little amount of bitcoin before,
It is when I just got started knowing bitcoin, I invested some bitcoin and put it on a wallet which I didn't take care of. That time, the value of bitcoin is below a thousand dollars, I just stored it and even forgot about it. When bitcoin started to increase its price, I tried to look for it but unfortunately, I cannot find or retrieve it ever since.
That was very common years ago when the price of bitcoin was low, people bought bitcoin and they did not thought much about it and they forgot about their coins but some time later they realized the price of bitcoin had gone up dramatically and they wanted to get those coins back but since they did not took enough precautions to recover those coins they lost access to them, however I believe such scenario is going to become less common as the value and the potential of bitcoin as a currency becomes more widespread to the general public.
True that, when things become worth more people consider taking more care of them as well.