So today i disconnected while playing Comp Team DeathMatch, Then reconnected while game was still going. Then we won that game, and when i went to play it again and saw that i had been suspended and lost around 70 SR. So basically if you disconnect, No matter if you reconnect or not, You will still get suspended.
This is normal. With arcade Competitive modes, there is only a 15 second return time from leaving a game (as they run very short in comparison to normal matches). To learn more about why disconnections are penalized please see this post from Blizzard:
But i was out of the game for like 30 secs. I DC then reconnect, then win that game and still get a penalty.