maybe it's not just your luck my friend
even if you're a programmer (I also am
) there's no way you can detect it immediately unless you're really a cautious person and not being a cautious is not a crime
just make a complain with paypal, sometimes the seller just don't care.
The problem is if the seller ask you to send it back there's just too much problem:
1. shipping (lost and damage) problem
2. the seller try to lure the time (I did, now I have 6 month unresolve case for +$100 item, it's too late to complain to paypal or ebay as I have no longer the receipt of shipping back to china, etc.)
if the seller is an honest ppl, that'll be fine...but it's rare lol