they are shared utilities but not shared components. that's why they are in separate folders.
the platinum folder and the sonar X3 folder. forgive its been awhile since I had multiple versions installed on one PC.
did you open your sonar/shared utilities folder (in sonar X3) and look for the VST scanner ?
I have to agree with Scook, I would try installing the x3 update right on top of what is there.