What you are actually talking about? I mean what do you mean that their Hot wallet is empty? That means you could not withdraw your money ? Or they refused your withdrawal? Yes, it's true that If people lose they will earn. And this is normal. So what is actually wrong here? They refused your withdrawal and forced you to play and lose?
I guess it is the same issue as what experienced by some other players:
https://bitcointalksearch.org/topic/i-need-admin-of-bitvest-to-come-here-and-explain-not-paying-my-winning-5359651
That are some other users who are also complaining about empty hot wallet in Bitvest. I look into those cases deeper and I can see that when the hot wallet is empty, withdrawal is not processed and players get a notification like in below image:
Image taken from cjmoles post here: https://bitcointalksearch.org/topic/m.57617797