The coloring matches no breed that I'm aware of. Lots of possibilities-- the breeder could have meant some kind of hatchery hybrid, a stealth rooster might have visited the breeding pen, or the breeder could've been feeding the buyer a line of you know what. I don't think that chick is any pure breed.The OP says that it was a named variety from a breeder but he/she has forgotten the name.
OP- Don't be embarrassed to contact the breeder and ask. It will satisfy your curiosity, and I'd bet the he or she wouldn't mind at all.