Lesson learned on the hard way, don't be lazy.

[oszika]

Many years ago I received a fishy negative feedback, smelled like a shakedown effort, so I started to look into the buyer and learned, he had a history of hitting sellers with negatives suspiciously frequently. I guess some sellers asked for revisions and offered a generous refund... By the way eBay didn't help, apparently they love buyers more than sellers.

After that incident I established a habit, when I received an offer, especially with lowball offers, always checked the buyer's feedbacks giving to others. Sadly many of them was generous negative feedback suppliers. Since, the first thing I always did, put them on the blocked buyer list, then let the offer just expire. As time passed I became lazier and lazier, started to abandon my habit... Bam!

Just got a negative from a buyer who is not hesitating to hit sellers, -in my case- after claiming something nonsense, then not getting a favorable response...  eBay didn't help as usual. This feedback doesn't violate the rules, even it's a proven lie. 

Now, back to my old habit.

By the way, today I just received an offer from a guy who quickly made it to the blocked buyer list. Now, let his offer expire... 

Lesson learned, don't be lazy.

[reallynicestamps]

"I regret  you are unhappy with your purchase. Please return it for refund."

Tells a future customer that you are willing to take responsibility.

And you can leave more than one Response so, if that is ignored.

"Purchase 10/10/23. Delivery 15/10/23/. Feedback 25/12/23. No return as of 6/12/23."

Makes the complainant look whiney and unwilling to be helped.

[toomuchstuffagain35]

And passes muster as "not negative". 

"Just the facts ma'am".

[mam98031]

Actually it is best to learn TWO lessons here.  You described your first one, the other one is you have got to be careful with your comments to feedback.  Your comment is more harmful that the buyer's FB they left for you.  That is not a good thing.  All your potential buyers see that and you should be aware of that and sensitive to it.  I see way too many sellers doing more self harm because of what they comment.

As to the FB problem.  When you talked to Ebay did you tell them that the buyer has a history of doing this with FB.  If you see from their FB left for others that they leave lots of negatives, that can qualify for FB abuse which is a reason to get your FB removed.

Another thing you can do is contact USPS [if you shipped through them], or whomever the carrier was.  Most if not all now take pics on delivery and that pic should show you if the packaging was damaged.  Get a copy of that Picture.

You didn't mention, did the buyer file a claim with you for a refund?  Most would if it is true because it would qualify as damaged in shipment.