I too was scammed over a trailer on ebay in the same circumstances as your friend,the police have failed to track em down and ebay do nothing it seems as there a couple of dodgy listings for trailers just about every week.I have written to Watchdog amongst others please suggest your friend does...
Seller had 100% feedback,gave serial number of trailer,lots of photos and I was sent an ebay invoice so seemed much more kosher than you seem to think!
As in the article written in Horse and Hound this week,I too regrettably was caught out by these scammers and would be very interested to hear from other people who have either been defrauded in this way or came close to it but backed out in time! I am now aware this has been going on for well...