Sounds like it could be a chargeback. In fact, I looked up your buyer and the account no longer exists. This suggests that your buyer was indeed a scammer and got some work done on Fiverr and then opened a Paypal dispute. It sucks that this happened, but alas it is the nature of Fiverr. There’s nothing you can do to stop it.
The whole “top buyer” thing doesn’t mean much. It means heavy activity or a lot of money spent. Sounds like your buyer just got a lot of free work.
Whatever work you did for him – go post it online. Make a blog or post it on your website or something. Make a post of the logo or images or whatever and say "Made this for a client who ended up canceling the order. This is 100% my work and I have not given permission for it to be used by anyone else."
If you later find that your buyer is using the logo or pictures or whatever on his/her site, you can report it to whatever agency seems reasonable (I’ve heard of reports going to Google and then Google punishes the site somehow, but I’m not sure how it works).
As for the warning on your account – ask Customer Support for the exact wordage you used or something. Say you don’t know what the warning is referencing and could they show you exactly so you’'ll be sure to never do it again? OR you could say “This person reported me and then did a chargeback; can I have an explanation as to why I’m being warned for their negative behavior?” Remember to be polite, though! Customer Support will not help you if you are rude!
By the way, when sharing screenshots on the forum you need to blur/mark out the buyer’s name; them’s the rules!