So sorry for your loss
I have had yorkies for over 25 years so have had some experience with a few illnesses, i have had a yorkie (tye) die from kidney failure and i have a yorkie (zac) at the moment in the first stages of kidney failure, tye had heart failure so it was impossible to see the first stages of kidney failure with him because of the water pills he was on so the first signs we saw was that he did not want to eat and would be sick, he went from weeing a lot to not much at all, he also had no energy and his back legs started to give away as they lose strength in them, if your dog had last stage kidney failure he would not of been able to walk around like yours was, tye had a blood test which showed he was at the end stage of kidney failure and we had to have him pts.....dogs in the last stage act and look like they are drugged because of the toxins building up in there body.....
Zac is in the first stage of kidney failure, his signs are weeing and drinking a lot but apart from that he is fine in every other way...he is now on a new diet so he is no longer drinking as much....
Over the years mine have all had things they are not meant to have (the joys of having dogs that can get in to things) zac eat a plastic dog toy when he was younger which was toxic, his signs were he drank loads, was sick and then started having fits, the toxin did not affect his kidneys it damaged his liver but with a bland diet his liver recovered back to normal...
Mine have also had raisins and all of them apart from my shih tzu have been fine, 10 mins after she had it she was sick but fine after.....
All of mine have had onions and all been fine apart from zac who had little eye flickers (small fits)....
All of mine have had chocolate and been fine too...every dog is different some will be fine with something and others wont...as you had given your dog one or two raisins before i would of thought that if he was so sensitive to them he would of had a small reaction to them then like been sick or acted ill.....
Also you said that the raisins where in his sick so his body had not absorbed them yet......
When tye and zac eat things they shouldnt my vet told me the good thing with little dogs is that they cant swallow anything big enough to cause a blockage so i cant see a raisin causing one....
Also is rare for small dogs to get bloat...its large dogs that it affects and you would of seen his tummy bloated....
To be honest a yorkie at 11 could of had cancer which you would not of even known about, i have had dog with cancer and they are perfectly normal until one day they might start being sick...having an upset tummy...panting and then pass away...... there are so many things that could of caused his death...even a nasty bug...one thing to remember is that you loved him and he loved you, you did what you thought was best and thats all that matters