The Fantom VS plug-in will not work with natively in a 64-bit DAW, like Studio One...BUT...there is a workaround that works brilliantly. There's an application called JBridge written by a programmer across the pond. It wraps 32-bit VST plug-ins into 64-bit shells so they can run in 64-bit DAWs. I just tried it with the Fantom VS inside Studio One and voila! It works!
The Fantom VS is a great synth, especially with the plug-in. It is integrated into the VS-700R so I highly doubt it's been removed. It is part of the hardware, not a removable card, so there would be no easy way to remove it (if it's even possible). If they're offering a good price, it's probably worthwhile. They may simply not know how to access it, which wouldn't surprise me at all.
Here's a link to JBridge:
https://jstuff.wordpress.com/jbridge/