Bug is simple. Enter a battle. Die before the match is over. Leave said match, enter another tank, and finish that battle. Upon returning to garage there is no longer the top bar alert of the previous (the one you left) match results. Furthermore, if you go into menu, news, notifications, the battle does not appear there either.
A twist. If you enter a battle, die early, exit, and REMAIN in your garage, when the battle is completed then the notification pops up on the top bar, AND it appears in the normal notifications section under the main menu.
Device is iPad Air and/or iPhone 6, both in latest iOS. But fwiw, this happened to all of my clan mates running various different devices. Feels more server side to me.