Hi Anita,
I do understand your grievances against the system, but it is not the feedback system you should blame nor the seller. I am not sure about the product or the problem you had wid it. I am just trying to guide you about the feedbacks.
That seller must be having selling manager in his account. with selling manager, sellers can leave stored feedbacks to almost all buyers pending feedbacks. Also these days eBay management is advocating that sellers should leave a positive feedback as soon as the payment is received.
This would have happened in your case. Also that seller could have written something bad and hurt your profile. But he did not do that.
Also if there was any issue with the transaction, report it to eBay and get it settled. you can avail the newly launched eBay guarantee program as well.
Regards