I was playing Quick Draft. Pressed play. Got a call, so I cancelled the matchmaking. In the 3-5 seconds it takes for the game to go back to the previous screen, it said "opponent found, but it went back and didn't take a life. I took the call. Then I played a game and won. When I went back to the draft event screen, I was down a life.
It's not the first time it's happened.
That's the second biggest issue after being manascrewed, which happens in about half the games in Arena.