I was in a ranked hero select and I randomly got disconnected from heroes of the storm, when I came back I realized I’ve been demoted and have to play 1 normal before another ranked. Blizzard, how about you do your job please and return my elo to me and remove this garbage punishment that your amazing client cost me. Because I did NOT LEAVE the hero select and I shouldn’t be punished for getting disconnected from your client while I had internet the entire time. So I know the problem had to be with battle.net. (I wanted to submit a ticket but I don’t even understand why is it so god damn complicated to do so…)
The client does not randomly disconnect you. That only happens if your connection between your computer and their servers disconnects you. This can happen due to circumstances out of your control, such as backbone internet infrastructure failures or even quality of service determining that your game packets are not important enough to transmit (which is legal in the USA last I heard).
From the server perspective they have no way to tell between a legitimate disconnect, such as caused by internet infrastructure issues, and someone intentionally pulling the plug out of local network infrastructure. As such they have to treat all such disconnects as intentional and so punish them accordingly. If people did not think of abusing such a system this would not be needed but sadly it is.
Your MMR will be returned to you automatically after some number of ranked games played to completion. A common number thrown around is 10. The MMR is returned each such game in the form of a positive adjustment where by a win gives more MMR and a loss loses fewer MMR until all the leaver penalty MMR has been refunded.