I seriously think you should do something about this, then.
Losing money or cards is a serious problem, but being able to prevent losing them is even more serious, as that is pretty much cheating. Won a match? Close the other window. Didn't win? Close this and save in the other one, you got your money back.
Besides I'm using my account together with my friend because it takes too long to get cards alone. If we don't even get a warning message that the other is playing or something, we'll lose cards to this.