Why was it "supposed" to be a Brahma? (I'm guessing you ordered Brahma online, a store employee said Brahma, a bin of chicks was labelled Brahma, you incubated an egg labelled Brahma, or something like that?)
Just off the top of my head, it could be a Brown Leghorn, a Welsummer, a golden Phoenix, or quite a few other breeds.
It was striped like a chipmunk when it was younger, right?
I think I'm seeing brown feathers on the breast--so you've probably got a female there (males are likely to have black breast feathers, if they're otherwise colored like that as chicks.)