I’m not sure how it happen…
It happened when I’m near winning and opponent simply disconnect from game.
What’s puzzling is… I’m being counted as lost 
And another encounter is, even when I have a chance to battle, it say I’m disconnected and counted as lost. Is this possible?
Known bug, will be fixed.
Sorry to hear that it happened to you as well. But it’s a new game, these things are understandable~
Had this happen to three guys in a row, while I was fighting. I had a pretty lame line-up. But because of the connection error, I won 8 battles in a row (three of which were because of the actual error, the rest was pure luck with my enemies, I guess). And was promoted to expert league. Shouldn’t have happened. It’s just frustrating when it’s happening to oneself. 'Cause let’s be honest, that’s not how you want to win/lose a battle