awww - Streak, soooo sorry to hear this news!
Condolences to you and your galpal!! :>(
Kitties don't get colds - it's a virus that is similar to Distemper - sometimes, younger cats can fight it fairly easily, but it is hard on older guys, like yours.
Someone had to come in contact with it and transmitted it - do you have other cats? Did your cat go outside - sit in the window and encounter a stray? Some are carriers, some are immune if they were born of a female that fought it and came through it...
If you have another cat, keep your eyes open for signs - if any of the signs start up, get to a vet asap - vaccines are sooo important but even at that, there is a wild strain that even vaccines won't help, but it does help to ward it off. It all depends on contacts with other kitties and it is an airborn virus, which makes it harder to fight.
If you do have another cat, it may be wise to get the cat vaccined just the same and clean the house - walls, especially windows, wipe down the couch - stuff like that - areas where your bud here would sleep is really important!!!
Everything would have to be detergent washed and disinfected with a small amount of bleach.
And if you do have another cat and symptoms start, the vet will give you a strong antibiotic - probably Chlor Palm - that helps their immune system fight off the virus. When they get this virus, any little bacteria can excellerate into something pretty serious, where as in a normal kitty, it wouldn't bother them and their immune system could naturally fight it off easily - but with the virus your babe had, anything and everything would affect it.
A Vet backed me where this virus is concerned, he agreed that there is a wild strain and not just in Alberta, it is everywhere - folks I talk to all over the world have mentioned the symptoms - it's because people don't vaccinate their pets, some breed and this doesn't help matters, some cats get abandoned, roam the streets, come in contact with it and become carriers... and other scenerios!
But tell yourself one thing, it's not your fault!
and if you have a sec, take a gander at what the vet said about the wild strain, it may help understand a little better (vulcan advocate article)
http://www.animals-alone.com/media.html even vaccined cats, who might have a weak immune system can catch it - especially older guys -
Again, sorry to hear the news - memories live on and love never dies!
take care