It sucks when you don't get to say goodbye

This is Duke. We got him about 5 years ago, when I was still in highschool. Duke had a rough start, he was found in another state, in a hoarder's house where dead dogs were found among about 15 living ones all sharing the same single bowl for food and water. When we got him, he was scared of everything, stayed that way for a long time, scared of lights, sounds, even his own shadow, but we showered him with love to make him feel safe and happy. I left for college about 3 years ago, and after coming back home for my first summer, he started showing signs of cancer. His toenail bed was corroded and completely covered in cancerous mass, he got his toe amputated and everything was fine again. Then this year, my parents call me routinely to check on me and update me on stuff, where I find out they found a mass in his chest. Then about 2 weeks later he's in the emergency vet with seizures, my dad leaves him there overnight and the vets said he was blind by morning, then just 3 hours later, he passed, before any of us could even get there, the cancer had spread to his brain in such a short time. It makes me so sad to think he was alone, I miss him and his dumb face he'd make when content, how he thought he was a lap dog, and when I came home that first summer he just laid his head on me and didn't move until I eventually did. It makes me cuddle my cat a little closer from time to time.