Planet X: PROBES Sent to Peek?

Per this 1987 statement by JPL’s John Anderson, one function of the
Voyager’s was to search for Planet X.

    In 1987, John Anderson at JPL examined the motions of
    the spacecraft Pioneer 10 and Pioneer 11, to see if any
    deflection due to unknown gravity forces could be found.
    None was found - from this Anderson concluded that a
    tenth planet most likely exists! JPL had excluded
    observations of Uranus prior to 1910 in their ephemerides,
    while Anderson had confidence in the earlier observations
    as well. Anderson concluded that the tenth planet must
    have a highly elliptical orbit, carrying it far away to be
    undetectable now but periodically bringing it close
    enough to leave its disturbing signature on the paths of
    the outer planets. He suggests a mass of five Earth
    masses, an orbital period of about 700-1000 years, and a
    highly inclined orbit. Its perturbations on the outer
    planets won't be detected again until 2600. Anderson
    hoped that the two Voyagers would help to pin down the
    location of this planet. ...

Was Pioneer 10 and other probes likewise sent to get a closer look?
Note it is currently heading toward the constelation of TAURUS, the
direction Planet X is currently riding, per the ZetaTalk Path diagram
(http://www.zetatalk.com/theword/tword03h.htm)

Ron Baalke wrote:
    Following its encounter with Jupiter, Pioneer 10 explored
    the outer regions of the solar system, ....  In 1983, it became
    the first man-made object to leave the solar system when it
    passed the orbit of distant Pluto.  The spacecraft continued
    to make valuable scientific investigations in the outer
    regions of our solar system until its mission ended on
    March 31, 1997.  When the mission formally ended,
    Pioneer 10 was at a distance of 6.28 billion miles
    (10.10 billion km) from Earth. ... Pioneer 10 is currently
    7.29 billion miles from Earth ... Pioneer 10's weak signal
    continues to be tracked by the Deep Space Network as it
    heads toward the constellation TAURUS, where it will pass the
    nearest star in about 2 million years.