That sucks, but there is a lesson for everyone here which is to never spend a cent on a PPI unless a tentative deal is worked out, at the bare minimum an agreement that you have right of first refusal at asking price for a period of a day or two. Otherwise, you may be just paying for someone else's PPI.
And that was an expensive PPI.
The best course to take, IMO, is to have someone local from this board or the PCA take a look at the car for free, (make sure that it passes the "smell test", etc..), before investing further time or $$. The local can also feel out the seller for you face-to-face and see if you are dealing w/ a POS like this guy.
Sorry to hear about it, and thanks for the heads up.