i had a few good opportunities in the late game to use my ult. i would get the bandage toss the i press r and nothing. is it broken. i've only tried amumu so far. it might be a gamebreaking bug. this happened at the 25 min mark. Thats how i died a few times when i tried to get 5 man ults. except i had no ult. it was off cooldown. if were my keyboard, you wouldnt see a bunch of r's
I know there's a very old bug where his ult appears to be off CD when it is not. It's made me go in and die on several occasions.
Is it possible you were against an enemy with the ability to silence you? Or maybe you were stunned and killed before you had time to activate your ulti? It could be a bug, but most likely you were crowd controlled out of using your ultimate. It sucks, but it does happen.
http://www.reactiongifs.com/r/crybaby.gif
EDIT - Looking at your match history, I see a 
and 
, they are probably why you could not get your ultimate off.
