But seriously at the distance planet 9 is suppose to orbit there would be so little reflected light that most (if not all) current telescopes wouldn't be able to detect it, assuming they know where to look. The area to search is vast and would require repeated observation to detect it, so it's not surprising that we haven't found it yet. Larger telescopes are coming online the next decade that should be able to detect it but we're still left with the problem of imaging (and reviewing the data) of the right spot of sky over a long enough period of time. I'd expect that if it's really there we'll find out in the next decade.