that really sucks. if he's a good guy he'll own up and give you your money back. i've personally been ripped off on this site more times than i can count and it really fucking pisses me off to see other people getting ripped off too.
i've had people send me "s13" speed sensors only to send me s14 speed sensors and not want to give me my money back for them not knowing the right part all the way to a freshly rebuilt motor with "only 500 miles on rebuild" only to have the thing die 50 miles after install because the fucking guys torque wrench wasn't reading right $1000 down the drain, without even a "my bad dude". then you have the "no shows" where you drive for hours and the dumbasses never show up.
I try to mostly buy new stuff or things that cannot fail anymore because most, NOT ALL, of the people on here are just douchbags looking to rip someone off, or so it seems. but i have also met a hand full, MAYBE 12, good people on here that are really honest and helpful, other than that, mostly douchebag kids that don't give a fuck about anything or your money. maybe try randomly asking members if they know the person and if they are trust worthy.
now this is just my opinon, but it is based on my actual experience here on TR, which is biased because i've had more bad luck than good luck on TR and try not to use the site. i do come here often though looking for good deals on new parts so i can't say i don't use the site for that. i hope you get your money back though. good luck. if not, i use the brick method! which is... i go to your house and put a brick through your back window and hope you won't rip the next guy off. either way i get the satisfaction of knowing that the money you ripped off from me goes to putting in a new back window in your ride! sounds kind of childish, but so is stealing from a good guy! GOOD LUCK