The price does adjust automatically, but since the number of lost coins remains unknown, it's impossible to tell how much of the price growth is higher market cap and how much is lost coins. Hence impossible to know the "actual" total value of all coins outstanding, just the value of all coins not lost.
For example, if it turns out that half of all issued coins have already been lost, the real market cap is only half what it's reported as. (Yes, if half of all coins got lost starting now, the market cap wouldn't necessarily change since the price would likely double. But there is no way to know if the price doubled because of speculation or lost coins.)
Yes I am sure coins were lost over the past 3 years. Especially when they were 100 btc for a penny, but at the same time I believe that the number of coins lost are a fraction of what you believe they are...
Perhaps the best way to phrase it, I believe FAR more coins were stolen than lost and stolen coins eventually show up at an exchange.