It was never available in RF 8. Closest was buying either the Horizon Hobby Edition of 8, or the add-on extra cost update of the same for existing RF 8 owners. Then you got the E-flite Apprentice S 15e, but the STS wasn't even on the market (real or for RF) back then.
Being a stock plane in Evolution, you'll need Evolution to get it. Not available separately.
