A bit off topic, but there have been a lot of topics about cats dying, going missing, or having to be put down lately. :/
Anyway, I have not had the experience of losing a companion like that, but I also haven't had the joy of having one either. It's got be tough. Heck, I was crying Niagra Falls when we had to get rid of my Guinea pig after having him for just one week (my mom and I had some major allergy issues with him). Well, I hope you feel better, I'm sorry. :/