I was shaman during the Event Map. I actually killed everyone and was not awarded the title 'Angry mouse'. I had completed the event map 4 times prior so I received 'Egg Hunter'. But this does not make sense, for I did not die as shaman, and no mice remained...I have a quote of the chat:
Thanks to Funnyllama, we gathered 0 cheese!
Legitaniw is now your shaman, follow her!
Workmistress has just unlocked the «King's Pastry Chef» title.
Pikalovr has just unlocked the «King's Pastry Chef» title.
Sunnyisepic has just unlocked the «King's Pastry Chef» title.
Funnyllama has just unlocked the «Egg hunter» title.
Type /title to choose a title.
Your new title will be «Egg hunter» after the end of this turn.
Phinixlove has just unlocked the «King's Pastry Chef» title.
Squirrelboyo has just unlocked the «King's Pastry».
As you can see everyone got titles and I was shaman. Is there a way to correct this mistake?

Sometimes other players appear dead on your screen when they actually didn't die. This usually happens when that other player is afk/tabbed out or has their game minimized. Most likely this is what happened in your case.

That still does not explain why I did not die as Shaman when time ran out, nor the fact that I got a title for a surviving mouse as shaman. Also, everyone I killed received a title.

Now this happened to me, too. For me it happened after I spawned my 4th cannon. Everybody got killed but about 10 mice or so got a title, I didn't get a title. It also seems we are not the only ones who experience this bug: http://atelier801.com/topic?f=6&t=794545&p=36#m720

To earn the title 《Angry Mouse》, you must kill all mice in the room by using 3 cannons or less before 00:15 is left in the event map. A tip to kill all mice more easily is to use sipirit. It creates a 80% possible chance of slaming the mice against the shaman objects or ground.