Encountered this bug again after I got interrupted by a call. Luckily I was able to quit the fight before my game crashes and so I did a little experimenting on Mirage stages. As it turns out, there are many ways for this to occur:
A) You get interrupted during gameplay.
B) You accidentally pressed the home button.
C) You accidentally pressed the back button.
D) You turn off your phone at any time during a fight.
E) You pause the game.
As it turns out, if you do anything that would pause the game, that would happen. So yeah, I suggest you to not pause during fights, especially in Fight Club. This has resulted in me losing games unnecessarily...