As already posted, a "hopper" is a young mouse with their eyes now open, also sometimes called "popcorn" for the way they bounce around. I don't believe you could talk
ANY ball python into eating a grasshopper, as BPs are VERY picky eaters & prefer warmed prey (lifelike, ie. "warm-blooded" prey). I think maybe you misunderstood them, but anyway, I'm glad he survived beyond their lousy care. Welcome...we'll help you sort this out.