There may be ifs, ands, or buts. Sometimes.
I have seen listings where the BIN persisted after a bid was placed. Not saying it happened here, just that it may be possible.
From the
eBay help page:
Buy It Now option: auctions
When you add a Buy It Now option to auction-style listings, buyers can either purchase your item right away at the Buy It Now price or place a bid. In most categories, the Buy It Now price must be at least 30% higher than the auction price.
When someone bids, the Buy It Now option usually disappears; however, in the case of reserve price listings, the Buy It Now option remains until the reserve price is met. In some categories, the Buy It Now option may continue to be available after the first bid for a limited time.