Keep in mind the idea of how long Planet X would be near when making the loop around our sun. If Zech is even close in his estimates, it would take some 400-to-900 years to cross Mars' path, inbound and cross it again, outbound... Based on the 3,600-year-orbit.
This would hardly be "in-our-lifetime" IMHO. NASA has been searching for this planet for several years and Sitchin has interviewed at least one of the NASA scientists. The video is on the XFACTS web site;
A little more can be found in Sitchin's articles, www.sitchin.com.
There are others but I forgot their names,,, will post when I remember them...