This happened to me as well. It crashed during matchup though - didn't start the game yet and they didn't match me up with anyone yet. The cancel button was still lit up. Game closed, I opened the game back up to find I lost one life.

Happened to me twice in one run, but it said 'opponent found' then never moved into the actual match. After a few minutes of hoping, I clicked exit and reentered the game. Both times I lost a life. Shame because it was my best run yet. Ended up with enough gold for another run, but I'm not so sure I actually want to risk it.