I've done a few hundred deals on e-bay, about equally split between buying and selling. I have a few rules of thumb regarding knife buying on e-bay.
1) look at the seller's feedback and READ the comments. Ignore the auction if the person has justified negative feedbacks. Ignore any auction where the seller says "item sold as is, all sales final".
2) make sure you see pics of the entire knife. I bought a knife on e-bay where the unpictured side of the knife was badly rusted. Luckily the seller was a good man (excellent feedback rating) and he did an exchange. From that transaction forward I always ask to see both sides of the knife.
3) send the seller an e-mail to confirm the condition of the knife. This serves two purposes. First, you get to learn something about the seller and give your gut a chance to evaluate the risks involved. Many sellers will volunteer to take the item back if you aren't satisfied. Those are the ones to do business with. Also, you will find that many sellers can't or won't describe their items in detail - avoid them! Second, it seems that 88% of e-bay sellers like to think that their items are "mint". Ask specific questions until you are satisfied with the "mint" rating.
4) trust your intuition. Don't give an item your highest bid unless you are fully satisfied you know what you are getting. Avoid bidding if you have any doubts.
5) withhold leaving feedback until the deal is done. Feedback ratings are your best leverage.
Send me the details of your e-bay issue and I'll work with you.
Bill