I agree with what lots of others have said or implied here - a sale advertised through AP has nothing to do with AP and AP can't in any way be expected to arbitrate or regulate. I reckon the private sales are a good thing for the forum. A buyer who buys without looking or getting an awful lot of detail from the seller - whoever and where ever that is - is asking for trouble in my opinion.
MartyJ's guidelines posted earlier (about 7 posts prior to this) in this thread and any form of check list / disclosure sheet suggested out of here has got to help - but so does asking questions, viewing or getting someone else to look.