There should definitely be vobs in this, are you looking into the right place? You should find your trees under:
objects/static plants/trees/tropical
in your obejct collections browser.
This, of course if ypou let the installer do the job for you. I never use the installer, I prefer to do my own thing with the zip files.
But if there is definitely no vobs, start a thread in the store talk forum at Corn.