Buyers are not able to cancel transactions. If you asked the seller, but still got a non-payment strike, they obviously cancelled the sale using 'buyer did not pay'. There is no reason why Ebay should remove the strike from your account. Many sellers do not want to sell to bidders who have two non-payment strikes so you will find your bidding and buying activities are restricted for the next year.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)