If . . .
If this is indeed a minor condensed star, consider the mass of the nebula that created it. Consider as well that stars do not form singly, but in packs of 10s, 100s, possibly 1000s. Consider the residual matter from such a star-forming nebula.
Tip of the iceberg indeed...
If this is simply a rogue gas giant, roaming between the stars, then there may again be many, many others on similar voyages.
WISE and Spitzer, and all others capable, will need to track this bit of flotsam to chart it's proper velocity, to be checked against that of the local neighborhood.