He was never found unworthy. He was simply not found right away.
Rev 5:3 And no man in heaven, nor in earth, neither under the earth, was able to open the book, neither to look thereon.
At that time, Christ was not in heaven, in the Earth or under the Earth. Likely he was still ascending up to heaven. As soon as he entered heaven he prevailed to be worthy: Christ "hath prevailed to open the book, and to loose the seven seals thereof."
Rev 5:3 And no man in heaven, nor in earth, neither under the earth, was able to open the book, neither to look thereon.
At that time, Christ was not in heaven, in the Earth or under the Earth. Likely he was still ascending up to heaven. As soon as he entered heaven he prevailed to be worthy: Christ "hath prevailed to open the book, and to loose the seven seals thereof."
I don't think it means Christ was not in heaven, but that no mere mortal was found worthy to open the scroll.