If I'm not mistaken, in your documents, along with the dreamtonics folder, you should have "Synthesizer V Downloads" folder which downloads the installer for the editor when you update, so whenever when you updated, it should have the installer saved and archived there unless you manually deleted it.
SVS now let's you have multiple versions of the same vb installed and you can select which version to use, there are unofficial archives of the installers around but afaik companies ( at least some of them ) can provide you with it too, if someone knows more about official distribution do contribute please haha.
Even if you can roll back the vbs in editor, it's still good to archive the editor installers themselves, because depending on the update, even outdated vb's can have different outputs depending on which editor version they're in.