My game in battlegrounds got disconnected right after I selected a champion. I lost 100 that time. It happens from time to time and it is kinda not fun to see your slow progress gone in one go due to the technical issues on the Blizzard side.
never had that problem, so how you know it aint your connection that is the problem.
Maybe it was my connection thus I reconnected immediately. However, I was already out of the game with -100 points.