In 2010, you came across a site that was giving away bitcoins. The site said it was free money so you signed up. You were logging in to figure out how it was money but couldn't. The last time you logged in you had more than 100 bitcoins. Later you forgot about the site until 2017 when a ponzi was advertising Bitcoin. Bitcoin? The name rang a bell and you stated hearing stories. You remembered you must have many bitcoins somewhere but you can't even remember the name of the site. How would you recover your BTC?
Lol, when I first heard that bitcoin was giving away thousand and millions of dollars to anyone that has held it before for a long time, and I was not sure if I ever bought as at the time I heard of bitcoin, because I must tell you that I really heard of bitcoin in 2010 too which I never paid much attention to even when they were giving it out free.
When I heard of bitcoin later, the first thing that I did was to start searching my mail to see if I have any related email to cryptocurrency or most of these Ponzi sites that I have joined before of which you must have surely link some to your email, so email is still the best bet for you to search through to see if you have participated in any of those projects, if you are not the type that threw a paper wallet away then.