I just assumed I had slept through the alarm and checked my phone. After consulting my good friend Google I found out it's not unique to my phone, it's an iPhone "disease".
But why would something as simple as an alarm just stop working? Solely because it's New Years? Sounds like Apple's own Y2K..
Well, who knows what happened - if you do, please shoot me a mail! ;)
It's said the alarm will be back to it's old self by January 3rd. Yaay! Nonetheless, for every important appointment I will always set a second alarm from now on. Better be safe than sorry.
Again, Happy New Year, especially to those who won't be woken up for the next two days.