Well now I get the crux of the conflict, (at least I think so) which is; The visibility of notification regarding scheduled maintenance. IMHO, mere publishing important notification which can lead to potential loss is not enough, it has to be properly visible. We can refer to a number of court decisions regarding visibility of traffic signs, where traffic violators are given benefit of doubt about not seeing a traffic sign because it was not visible. 
Having said that, I am no one to decide arbitrarily what is proper visibility and I do understand the highly subjective nature of visibility, BUT still I think there are some characteristics of proper visibility, for example it has to be on the front landing page of the casino in question not in the collapsible chat room window. The casino should have informed every player via email as well for proper visibility because it is possible that many players have active trading sessions, and they might not have felt the need to check the website frequently. 
Failing to satisfy above bare minimum standards for visibility can support OP's claim for compensation.