It seems to me that those who lost Bitcoin in those years tried or even could have returned access to their wallet. Because to restore access to today is not a big deal because all the data are assigned to a real person, so I do not think this is a problem. But to trace all operational data on financial operations. And this is certainly possible.
It is not possible to restore your coins if you are not having the private keys and the coins lost are lost forever ,tracing the coins does not get you to the coins and it is not possible to remember the wallet address in the first place if you are away for a long time.So be careful when you are dealing with crypto currency because if you forget to take back ups it is a waste of your time and resources.