I tell you what happened to me:
I was playing arena and i think I was 2-2.
In the 5th game, I got disconnected. I'm not 100% sure about the type of disconnect, but I got kicked out of World of Warcraft at the same time.
I was still able to surfe in the internet. My internet connection was good and the router was fine too, so I think it was a battle.net issue. Or maybe i got dropped by the opponnent?
Don't think so.
I immediatly entered hearthstone again and clicked on arena. My stats were still 2-2. So I didn't recieved a loss. And now I was still able to start a new arena game.
So I Did. I won it and I had 3 wins. But after those 3 wins, my arena journey was immediatly finished, that means, i got my rewards.
Summary: I was 2-2. 5th game went bad, would have been a loss. I got disconnected(randomly battle.net disco) and was able to start a new game, won it and ended up with 3-3 instead of 2-3.
Since every game which is won results in better prices, I think its quite an option to just disconnect youre battle.net when you already have 2 loss + its obvious you will loose the game.