I reached out to the buyer and they said they left it in error and would "try" to retract it. Well, of course they made no effort to do it
No amount of effort by the buyer would have helped. You must make the effort by sending a feedback revision request to the buyer. That is the only way a buyer can revise feedback after it is left.
I have asked them this before and never a satisfactory answer as to why eBay allows buyer feedback to be left at all if no money ever changes hands?
Because not all sellers are innocent when no money changes hands. Sometimes the seller behaves in an unscrupulous, unethical, or abusive manner and the buyer deserve a chance to warn others about it.