i have had some issues, but with less expensive items from sellers from hong hong, like three times they do not send me all the items i bought from them, but i contact those sellers as they were stores, they really are concern about theirs reputation, so they eventually send me all the items, i even get a free gift :), so try to contact the seller and explain your problem,
of course when i buy from ebay i always buy from top rated sellers, i don´t know if that is your case, is it?
Did you pay via paypal? Ebay cover buyers WAY more than sellers...Sellers who know the rules will sort things out as they know they will lose out. Message through Ebay to supplier. If they dont resolve. open a case. If they still dont resolve. You get your money back. Make sure you save all correspondance. ALWAYS communicate through Ebay I had a seller sell me a duff Nex 5 a year ago. He denied everything..refused to take it back. I got refunded and kept the effed Nex 5.
I have done all as listed above- and its all cool now- seller has gotten back to me- seems that they 'forgot' the lens (well it is REALLY REALLY TINY)... (just a bit worried as the seller listed themselves as offline for the next 2 weeks) #$#%! (I wana have my 14mm!)
Ok- in true DrEvil style- I was really sad for a few moments, but then it was all ok. But those few moments were really bad!
I guess that's why there are all these "unboxing" videos - so you can show that the goods were / weren't in the box. I do one whenever I get something expensive to prove if things were missing or damaged on arrival.