hmmmm I don't remeber a bouncy thing... mabey the key is hidden somewhere in the room... If there are any pots check under them... or mabey you already got the key and don't remeber? Beats me. But I would assume that since "Every walkthrough I've seen says you get a key when you kill it." I would assume that you got the key and just don't remeber it... or your in the wrong room.(or you only read one Walthrough.)

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"Science is the poetry of reality." ~ Richard Dawkins