Feline Infectious Peritonitis (FIP)

I lost my little Buddy Sunday a week ago. He was a very sweet black and white Cornish Rex who was only 12 years old. We'll never know what happened, but it was relatively fast. He had started loosing weight, then on Thursday evening he tried to jump on the bed and never made it. I put him on the bed and when he got comfortable in his blanket he let out the most horrible pained sound three times. He was still eating a little wet cat food (which had been his absolute favorite!) and would drink water if I put him in the sink (his favorite watering hole). I took him to the vet Friday morning and they took blood, gave him B12 shot, fluids and sent him home with no diagnosis. When he got home that afternoon he ate a little wet food and drank a little water (for the last time). He was peeing in the litter box, but missed each time. Then it looked like he was straining to poop, so I thought maybe he was constipated. Also, he was very weak--he'd have to lay down after walking a short distance. When I picked him up to go to the vet on Saturday he was limp as a wet noodle. He had a fever, they gave him antibiotics and pain medication and a gel enema and fluids. The X-ray did not show any blockage. He had pain if his tail was raised. This may be why he couldn't get in the right position to poop or pee correctly. The blood results were mostly normal, white cell count up a bit, but they said it would be a normal stress response. They gave me antibiotics and Meticam to start Sunday morning, but he didn't make it that far. At home, still no eating and no drinking water even though he tried for awhile in the sink. He got weaker and weaker and called out several times. He peed again, but I didn't see it, but he missed the box again (and when I say he missed the box, he was in the box but his aim was bad). Poor baby still had the instinct to use the box, but couldn't do it right. He got up one last time and seemed to be headed for the box, but stopped. I picked him up and put him in, but he could just barely stand with his legs akimbo. I put him back in his bed and at some point he cried out 3-4 times. I tried to give him water with a syringe and a little food, to no avail. Probably about 4:00 AM I noticed that he was laying flat out and he had vomited and he would twitch every once in awhile and let out a breath. I knew this was the end. I rushed him to the emergency vet and they were so kind. His heart was still beating but he was non-responsive and had brain damage. When they wheeled him in to me for the final injection I could see one pupil very large and one very small. His little body would not give up, and he seemed to be struggling for air (his mouth wide open and his tongue contorted). Finally it was over for him. You know how the Rex has those large ears? Well, his were erect and his eyes remained open, but his little mouth slowly closed. I think he probably had a stroke or threw a clot which went to the brain. Hindsight, 20 20, I probably should have just stayed home with him and he would have died before long. But I was alone and it just seemed the thing to do to bring him to the emergency vet. I don't think he was really in any pain--basically brain dead, but...I've never been with anyone (people or pet) that died like that, and I've got to say, it's not pretty. I remind myself that it was just his strong little body, trying to do what it was programmed for, and HE was actually gone, but it was painful to see him like that. I guess we'll never know what happened. He took a bad fall on 7/13, but seemed okay. The weight loss hadn't gone on for long, though I can't really remember the date I noticed. But by 7/22 (Thursday) he had acute pain and I think that the bad aim in the litter box may have been an indication of some brain impairment, and his inability to drink from the sink (even though he tried), the same. Lesson learned, be alert for the sudden weight loss and don't try to rationalize it. A good eater who suddenly won't finish his plate means something important. And I wish I had pressed them more at the vet on Saturday. I think that's when he should have been put to sleep. But I guess they just didn't know how bad off he was. I've tried to do a little internet investigation on what might have killed him (yes, I know how sketchy the internet is for this kind of thing, but it's there to tool around in). Buddy suffered from a chronic respiratory problem (in fact he left the breeder a little later because of a severe case and came with a torn third eye thingy). It was not unusual to wipe a brownish red tear from his eys, and his frequent sneezes often contained brownish red mucous. I'm seeing the vet in the morning for Kinsey's dry skin which has gotten worse, and I'm going to ask him about Feline Infectious Peritonitis (FIP). This site gives a good description if anyone is interested: http://www.animalhealthchannel.com/fip/symptoms.shtml
Has anyone else had the unfortunate expierience with either "wet" FIP or "dry" FIP?