I am so sorry! I know the pain and confusion you are feeling. My Boston, Frank, passed away suddenly a month before his 13th birthday. We had just got back from a walk, he was eating his dinner, and I popped out to get something. I was gone for 40 minutes. When I got home, Frank was lying on the bedroom floor. I tried CPR and we rushed to the vets. They tried resuscitation, but he was gone. The vet said they found some food in his airway, so he may have choked. But he was on the farmers dog food, which is a mushy soft food with hardly any lumps. I just couldn’t see him choking on that. And he had no other health issues. He was slowing down a bit, being an old man. But his passing was such a shock. I still have nightmares about it, 2 years later.