Not being listed means that the Chrome uninstall routine was not registered with the control panel. I can't speculate on why or how that happened.
I would recommend manually deleting the Chrome folder. Right-click the icon on the Start screen, go to "Open File Location", which opens where the shortcut is inside the Start menu folders. Right-click that again, and once more choose "open file location", which will find the real chrome.exe (not a shortcut). Go up one level and delete the entire Chrome folder.