Dude sure, yeah the bidder was likely lying. So? File a NPB and move on. But leaving “negative/positive FB” you have violated the rules in a manner which can be seen by all.
And, you’re not 'warning" other sellers. That is a load of crap that sellers have been pushing for years . Other than blocking a few buyers, sellers don’t get to pick and choose who bids on their auctions. Nor do many check out bidders unless the auction is going crazy high. And, even if they did check out a bidder and did see a “warning” there is not much they can do. So, that’s bullshit.