I originally thought nobody would try brute forcing simple keys like this, but then the person who found the vulnerability did it so I bet other people have done it. It's less "gee hope this works" and more "If someone screwed up there key generation this might work," and screwing up key generation is a known problem. Rare, but it does happen as this case demonstrates.

Almost assuredly someone is brute forcing all single-byte keys. In fact the private key equal to 4 is a single-bit, or "one hot" key, so an attacker could have found it by brute-forcing 384 different keys 😂