CGC has omitted this information on so many minor firsts and cameos it isn't funny. Then again, that's not what you're paying them for.
He has a cameo in 27 and in 28 he is front and center on the cover and it says "ENTER STARHAWK!"
Maybe CGC considers 27 his first full (OPG does not), I can't find any slabs of 27 out there.
Neither could I.
Yes, CGC has omitted a lot of this information, maybe to protect themselves from a character popping up in a panel somewhere.
Starhawk has a page in #27, but I can't remember if he is called out by name. I don't think he is.