It’s estimated that about 20% of existing bitcoin is unrecoverable so it’s not really a stretch.
Discussion
Theres obviously no way to quantify how many people around the world tell stories about owning Bitcoin pre-2015 that they sold, lost, or spent on drugs, but if there were, I’d be willing to bet 99.9% of them are lying.
There's no way to estimate
It's just guesstimate