Am I wrong to think that I should get at least most of them back..... It was my mistake, so if there was some penalty, I guess I would understand, but it just seems like it's my money, that was sent to a casino site by accident, so it should just be returned?
Yes, you're wrong to think that they should return your funds. It's your mistake, you're the one who placed a bet by accident. Shit happens, move on.
I'm trying to see it from the other side anyway i can, because what if the bet would have won? Would mbitcasino return the money they just got for free to the owner?
This is not relevant as you didn't win.