I've been buying and selling on eBay for many years and can give you a few tips that will minimize future grief such as this.
The first thing you want to do when you look at an eBay product description page is to check the seller information on the right side of the page. Never buy from a seller with fewer than 100 feedbacks. Never buy from a seller with a positive feedback rating of less than 99%. I've sold thousands of items and still have a 100% rating. Anyone with even a 99.2% rating isn't trying hard enough.
Good sellers make sure they don't sell faulty merchandise and will make good on any problem. If you have a problem, contact the seller through eBay. They should get back to you with an offer of resolution. If they don't, they're asking for a negative feedback.
If you order from an eBay seller and don't receive the item after about 4 weeks, click through eBay's channels to contact the seller about it. I did this recently and received a refund then next morning.
That all said, clothing shopping online is always a bit of a hit and miss situation due to size issues (no matter where you shop). To be honest, I only buy less expensive clothing items on eBay, and even then avoid anything where size is very critical, such as jeans or, as in you case, a skirt. Try to buy from sellers who clearly state a return policy in their descriptions. I do that with all of my sales, but, sadly, it seems to be less common among clothing sellers on eBay.
EBay is great for shopping for many types of things, but with clothing, be prepared to score a worthwhile item at a rate of maybe one out of every 4-5 tries. If you do find a good brand or item, try to buy several, as I recently did with Hanes t-shirts (Hanes has a good eBay store). In fact many of the big manufacturers and retailers also operate eBay stores that sell nicely discounted items and often have free shipping.
