Yes, this has been heard of. It's called a classic 'too good to be true' scam. 'A mistake made amongst the group'? 'Recovery trade'? That's just more bullshit to squeeze you dry. You got lured in with small, 'easy' wins, then hit you with bigger and bigger demands. It's the oldest trick in the book.

So, yeah, if what you say is really true, you got scammed. And frankly, the fact that you're still trying to justify it tells me they've got you hooked. Just walk away. You're not getting your money back.