Did you initiate and complete the attack? or did the app crash before that?
I made a post about the former a couple weeks ago, you’re not alone either as is evident with the amount of replies:
Unfortunately there isn’t anything they can do. All they tell you is to make sure your internet connection is good.
I would also say that if you notice that the game is lagging or not running smoothly, just don’t bother attacking in war. Just restart the app yourself and try again later. I’ve noticed that I’ve ran into these war disconnection or crashing issues when the app starts freezing on my end, e.g. at the summon gate the app takes its sweet time to give me the hero I summoned, then when I tried war it crashed and gave me 0 points.