Did you ever get this resolved?
 
I thought the default installation installs both VSTi and VST3.  That means that Ableton needs to be pointed at the correct folder for the VSTi file with the .dll extension.
 
In my set-up that's ...cakewalk\vstplugins\Rapture\Rapture x64.dll, but the file name depends on whether you've installed the 32-bit or 64-bit version.  (Mine's x64)
 
If both VST versions (2 and 3) are installed, the presence of the VST3 file shouldn't have any impact on your VST plugin operation.  By the way, the VST standard 2.0 is often just referred to as VST or VSTi.  I think they are all interchangeable.
 
 

If Abelton does not use VST3 plug-ins then the VST3 isn't your issue - they are different file formats.
VST3 plug-ins have a "vst3" file extension, for example Boogex.vst3
VST plug-ins have a "dll" extension for example Boogex.dll
 
A program that can't use VST3 plug-ins just doesn't see them because it doesn't recognize the file format.
More than likely your Rapture VST2 plug-in is just in a location (for example C:\Program Files\Cakewalk\Vstplugins) that you don't have Abelton set up to scan (search in).

If you still can't locate the VST2 version search your hard disk for either "Rapture.dll" or "Rapture x64.dll" depending on if you want the 32 or 64 bit.  Once you find it either set Ableton to include that folder in it's VST scan path or copy it to where Ableton will find it.