That is big capital you lost there. 0.5 btc is over $20,000 at the current price and it is not funny losing that kind of money. When I read that people invest that big online i feel they are taking unnecessary risks because that amount can be easily lost and that is what we have seen here too.
There is always a way to force them pay you back but just that process is cumbersome which might lose money the more again.
That is the problem and that makes it look like victims do not want to go on chasing those who scam them. They do not want to waste money or be scammed again by those who will promise to help them catch the scammers but in true sense of it are only after their money too.