DislikedGoMarkets is a STP broker so they make their money through spread. Because of this you can't expect them to refund you slippage.
I know you don't want to hear this but seriously, I don't see how a business can take onboard losses that they have no control of, it's different with non STP's as they make money trading against their clients so slippage refunds no doubt come from client money anyway.
From what I can tell It's not only us traders who've lost out, gomarkets have probably lost heaps now that all the EA liquidity has been squashed.
The best indicator is price.