Firstly, no buyer ever has to contact you prior to leaving feedback or for any other reason, and its not "rude" if they dont. They are buyers, it is their perogative. Dont play that card, it makes you look bad.

At the bottom of this page theres a link "Help & Contact". Click it.  It will give you a list of options - if you find and click on the "removing feedback" link it wont give you any option to contact Ebay. So, what I do is click "Report a Member", then click "report inappropriate feedback". At the bottom of that page theres a blue "contact us" button. click it. At the bototm of that page is a "Email Us" button where you can email Ebay with the issue.

Or just go HERE.  if that link doesnt work for you, just go to the contact and help button at the bottom of this page and click random things until you find an email option - thats what I usually do Lol

Make sure you include the buyers ID, Item ID / number and the issue - remove all emotion and keep it professional. If the feedback violates EBays policies, they will remove it, if it doesnt, they wont.

I recommend asking them to remove the DEFECT, not the feedback, because they are more likely to do that. The DEFECT is what actually affects your score on Ebay. The neg feedback will eventually disappear in all the positive feedback you receive.